e.Blue
Ironically, this may be changing soon as Microsoft is finally finishing up a brand new Thunderbolt audio stack which is based around USB 3.1/C and promises to greatly simplify what developers need to do to get their hardware up and running on Windowa 10 PCs.
We have true "PCIe via Thunderbolt support" (right now) under Win10.You have to be running one of the latest Z170x or X99p chipset motherboards that supports Thunderbolt-3 via USB-C port. It's now up the the audio interface manufacturers to create the appropriate drivers.
The reason for the "lag" on the PC side is simple:Thunderbolt provides access to the PCIe bus (nothing more nothing less).
We've had (and still have) PCIe slots on the PC.
The only way to access the PCIe bus on any current generation Mac is via Thunderbolt-2.
This is why Apple is pushing Thunderbolt.
For PC users, Thunderbolt brought nothing new to the table.
Someone here put it eloquently. "Thunderbolt was a solution to a problem that didn't exist."
In their infinite wisdom

, Apple took away PCIe slots and gave their users the same features (albeit lower bandwidth with TB2)... at significantly higher cost.
ie: A Thunderbolt 1TB conventional HD is $200. That bare SATA drive is about $60.
It's easy to see the figures for Thunderbolt audio interfaces and get seduced by the numbers.
But... we've had those capabilities via PCIe audio interfaces for *years*.
MOTU 424 PCIe is an exceptional low-latency performer... as is the Lynx AES-16e/50... as are the RME units.
The only difference is you can connect the Thunderbolt units externally. That's their only advantage.
MOTU now has a "PCIe via Thunderbolt" driver available for their AVB series (for Windows 10).
You'll need a USB-C to Thunderbolt adapter (about $80 - just released this month and out of stock at most places).