Tony I went back to listen and no, it is a different mix. I also recently got a copy of the Laserdisc rip of the film and checked too. Oddly enough the LD mono track is different to the VHS mono track.
Yes, all version have a second chorus after the first crescendo, but only the Mono VHS (and LP) mixes have the second chorus as loud as the first. All other versions including the mono Laserdisc, have the second repeat much quieter and distant than the first.
Speculation: The mono mix is the original recorded volume of the chorus, i.e. the final crescendo and fade out are all the same volume as sung. The stereo discrepancies might be a lost notation for maybe a rear pan or fade out instruction that ended up getting baked into the stereo mix as a reduced volume fade out.
- VHS Mono/ 1961 LP mono: no fade on the end of Ave Maria
- LD Mono/VHS Stereo/all stereo mixes: fade on the second chorus repeat of Ave Maria
Listen to all the versions here. They are labeled for each source. Compare the waveforms if you have to and see.
It may not matter much in the grand idea of things however it is just one of the many peculiarities surrounding Fantasia that keeps me interested.