This explanation loses me at "infinity per dB" ... and I'm an EE. I think you're trying to cover too much ground here, it's really confusing to try to understan

This explanation loses me at "infinity per dB" ... and I'm an EE. I think you're trying to cover too much ground here, it's really confusing to try to understand what you mean. I believe the comment you're responding to is talking about the analog filter that is needed to avoid aliasing -- as the first words of your comment correctly note/explain. And in particular, the original comment seems to be noting the phase distortion (in frequencies near the cutoff) that analog brick-wall filters will cause. This has been a design contention for decades, really, ever since the CD format was introduced. It's a big design space, with options for gentler analog filters, followed by very fast digital sampling, and further tricks with filtering in the digital domain, where you don't have to worry about getting great capacitors, etc. It may be out-of-scope to lay all that out in one paragraph!