I'm curious. Is are these Hiz inputs impedance matching as if your pluging into an amp?

It might not be exacly the same, but it should be in the ballpark. There's variation in instrument amps as well. Most inputs I've seen between 75k and 4 meg were referred to as high impedance. 300 - 600 ohm inputs are low impedance and are often transformer coupled, in something like a vintage LA2A compressor.
 
 

Your typical audio interface's "Hi-Z" input will not be as high-impedance as a guitar amp, but high enough to not matter most of the time.
 
Oddly, many audio interface manufacturers seem reluctant to come right out and say what "high impedance" means on their products, so I've seen few specifications for them. I would expect, however, that it'll be at least 10K ohms. A tube amp will be 10x that.
 
So, as I suspect you suspect, there will be a little more loading on your guitar's pickups going straight into the interface compared to going into your Fender Twin. It's one of the reasons DI boxes are used when recording direct.

 For anyone who has a Motu interface most likely the specs are similar on their other models. I contacted Motu and asked for the spec on the Hiz and headphone jacks.
The headphone jacks are between 16 and 600 ohms. The HiZ is 200K.  I wasn't expecting 200k.