That's good info to have. Hope it works for you.

Well today I thought I'd give it a go and I just opened the "my Account"link and the Products link showed all my purchases from the past and plus the new- Sonar Professional, Melodyne and AD2. 
I opened the Sonar Professional tab and there is a list of stuff. I highlighted just the Professional and it opened a download link button.  
I started the download which was going to my normal Chrome Download folder but it kept stalling at 200 MB. I tried 3 times and it stalls at the same place. It says Unknown Network error. So  I think your right and they have changed something to tighten security.  Why a hidden download folder??   
The command Center has a buggy updater. It said there was an updated version but it just kept showing a circle going round and round. I tried twice.  I had to download the new version manually from the web site. 

FWIW, I installed Platinum exactly how you just described. All went without a hitch so I'm not sure about any tightened security.

Command center does indeed notify you if an update is available as well as check the downloaded file to verify it.  It does not keep the data from a download that did not complete to allow you to continue where you left off. I starts over each time.
 
If the file is small that's not a big issue. If on the other hand, like me, your connection is metered it's an additional expense.
 
The only issue I can see with the offline install is you need to verify the hash on the download if you want to verify the file before beginning the install.
 
I created a post in the  Features & Ideas Forum suggesting they add a download only option to the command center. 
 
If you think that is a good idea go and vote on the suggestion. They say the more votes they more likely something is to get implemented.
 
Cheers

They just need to add a download but don't install option.

Here is a subsequent response I received from CW support.  I must've missed this download link he's referring to, despite looking several times previously.  I'll try again tomorrow night when in front of my DAW.
___________________________________________________
"If that will be easier for you, you can download the same installer files by logging in to your SSO account, then going to the products page.
Under "Connected Products" you will see SONAR Platinum and others listed. If you click the product name, you will see it expand, and at the top of the expanded view, you will see " Select a product from below to generate a download link:"
From there, all you have to do is select the product (or sub-product, in the case of SONAR Platinum) and an orange "DOWNLOAD" button will appear in the lower-right corner of the expanded window.
Once you have downloaded all the necessary installers, you can place them onto a USB drive, and then transfer them from the USB drive to the offline computer."

Yep, that's how I did it.

FWIW... I have a slow internet connection in my studio as it is a fair distance from my access point, but I really wanted command centre to be able to check for updates. If you download and install the files directly without using command centre it does not detect them, and can't check for updates. My workaround was to downloaded the install files to a flash drive from my Cakewalk store account, then place them into the download folder inside command centre on the studio computer (this can be set to any folder you like using the command centre settings). When I opened command centre to install the files, it simply vetified the files that I had placed in the download folder and installed them. Now I have lovely green lights to tell me that I am up  to date and it didn't take a fortnight to download:)
 
 

tenfoot
FWIW... I have a slow internet connection in my studio as it is a fair distance from my access point, but I really wanted command centre to be able to check for updates. If you download and install the files directly without using command centre it does not detect them, and can't check for updates. My workaround was to downloaded the install files to a flash drive from my Cakewalk store account, then place them into the download folder inside command centre on the studio computer (this can be set to any folder you like using the command centre settings). When I opened command centre to install the files, it simply vetified the files that I had placed in the download folder and installed them. Now I have lovely green lights to tell me that I am up  to date and it didn't take a fortnight to download:)
 
 

Thanks.. this is good to know.  I'll feed this back to CW support.  Hopefully they can push their developers to come up with something a bit more strategic within Command Center. 

my daw has been offline too. i have windows defender, and when i go online i update it. i have to be online for xln, so it really is no big deal to do so for sonar as well. i don't do any surfing, just dl what i need, then pull the plug. best of both worlds, i think.