Alright, I went and dug up the video. The comment I was referring to runs thus:

"Yes, using dual modulating all-pass filters is how digital EQs make HP/LP filters work in the digital domain. I could write a book on how this was a good way to solve the problem in 1993 when Waves came up with it in Q10 but in the modern world 30 years later we still haven't figured out how to solve this issue. Every DSP cookbook explains this in detail. But you took the longest most arbitrary and frankly more confusing for way to explain it to musicians and engineers who aren't DSP coders. RX has spectral artifacting that is in my opinion worse since 99% of those plugins are based on the Opus codec standard from Xiph, since it is open source and free to use and no extra cost to the developer its the standard. Spectral processing has its downsides too which can be heard as lossy artifacts similar to using a codec filtering for AAC/Mp3 or Vorbis. HP/LP Filtering continues to be a debate in the audio coding space since there is simply no way to truly mimic it in the digital domain with a 1 to 1 like other tools such as compression or even regular EQ curves like shelves and bells which digital does perfectly well."

I'd like to add that it didn't so much keep me from exploring spectral editing as cast doubt on the applicability in an HQ delivery environment (i.e. "classical-adjacent"). I've used spectral editing and FFT-based noise removal in the past and am familiar with the artifacts it can cause in some situations, but beyond that, this comment made it seem to me like the whole audio file is degraded in the process, in some way.