If TRs data analysis model is based on people not throwing in a massive finishing sprint and you're wanting to use TR to train then it seems pretty silly to counter their advice just for dickswinging watts on your FTP.
This is an interesting article on a few different options though:
Ramp test based ftp tests are designed to work with seated efforts only - standing skews them.
For training efforts, do what you want though.
I normally only stand for <30s efforts or perhaps for a few pedal strokes on long 10min+ efforts