How would it not run faster, given that otherwise CPU had to shoulder the rendering entirely, in addition to everything else? Even high-end CPUs at the time would struggle with that, especially with resolution and bit depth being equal. IIRC the original Quake didn't even allow more than 256 colors in software rendering for this purpose, and even then I recall having to run it in weird resolutions like 400x300 to get framerates comparable to what Voodoo owners had for 640x480x16bit.
The Voodoo was the indisputable king of 3D accellerators back then. Not everyone was running GLquake with a Voodoo card in their PC though.
I had an S3 Virge in my PC at the time. It was quite possible to get GLQuake running using a Direct3D to OpenGL wrapper, but damn it was slow. It sure looked better than regular Quake, but it wasn't really noticeably faster than software rendering.
