I agree it screws up the TSS and IF.
But if you are using Training Peaks, and your FTP setting is correct there, you will just get the raw power data ported over. TP will do it’s own calculations of tss and IF based on the stored ftp there. Your TR calendar would be screwed up though.
There is also another subset that could do this. Those who don’t care about the tss and stuff. If you are the kind of person who just loads up the next workout and doesn’t care about the all the fluff.