The last version of Vegas Pro to support 32 bit OS Architecture was terminated on November 9, 2012.
As far as beginning to learn about color bit depth and Integer vs. Float Point Math, the internet is a bountiful resource.
32 bits per channel float processing supports up to 79.2 Octillion colors (that's 27 zeros). The most we mortals use is 8- or 10-bits, or about 1/4 if that bucket.
He might be legitimately referring to the back end processing which does seem to max out with 32-bit floating point storage and processing. If project settings are any indication. As opposed to 64-bit integer or double-precision supported by 64-bit cpus. I assume the answer is that the performance penalty and increased memory requirements might not be worth the quality gain. Fwiw, I don't think any video NLE's do that. But a growing number of DAWs do and the improvement is self evident.
@manny-g You are probably confused as to exactly what is 64bit / 32bit windows computing architecture and 8bit / 32bit Video Color Space...... Or asking why Vegas does not now have a 64bit Video Color Space (Video Level) which would be very, very odd. No NLE has this.