Hi,
According to 3dMark 2000 this rumor is not true.
There is a significant difference on Win10 between hardware and software T&L. E.g. in 8 light High polygon count test the difference is more than tenfold.
Although it seems there is an interesting difference between Win10 and WinXP/7 but it's not hardware T&L related. On Win10 it seems there is no native 16-bit rendering. On one hand 16-bit rendering is much slower than 32-bit (this is just the opposite on WinXP/7) and in Game1 Helicopter tests (sky and clouds) it's easy to notice that the typical 16-bit color banding artifacts (because of missing 16-bit dithering, very noticeable on all DX10+ hardware) are completely missing (they are present and very rude on WinXP/7).
Test system: OS: Win10 64-bit, CPU: Phenom II X4 down-clocked to 1GHz, GPU: Geforce 960 GTX
Result with hardware T&L:
3dm2000_HWTL.jpg
Result with software T&L:
3dm2000_SWTL.jpg
On my Win10 by default 3dMark 2000 was FPS capped by forced V-Sync so I had to apply a compatibility patch (attached).
Win10_FPS_Fix.zip