This is a really good point.

I’ve also found myself messing up the run back but committing to the fight anyway with a few masks down. You can either heal back up by breaking the cocoon, or practice starting the fight low and keep the silk for later (one of the best changes from the first game IMO is making the cocoon an asset in contrast to the ghost that would harass you).

Another aspect is the run back itself. When you struggle a lot with a boss (as I often do), you will have to do the run back so many times that you passively start getting better at traversing the map. And even if the specific combos you used on the boss itself don’t necessarily translate to other bosses, the movement skills likely will keep being useful.

Didn’t personally watch the interview in question (or forgot by now) so I don’t know what they meant, but it definitely feels like lore wise Silksong can stand as an independent game with what I’ve discovered so far.

Regarding difficulty, Hollow Knight isn’t the only game that could have prepared you for Silksong I think.
I think what it helps a lot with is familiarity and mindset. The overall game loop is very similar.

That said, I think it’s wise to give HK a try before buying Silksong. It’s a cheaper game, worth playing through if you’re into these kinds of experiences and if you don’t enjoy it, chances are Silksong will not be much fun for you either.