So, several things...Respectfully, the post was about getting feats at/near character creation. When you talk about getting subclasses before feats that's not the case in what is being discussed.
I in no way was advocating or not advocating retraining subclass. But that's a choice that a brand new player will make (again, baring exceptions) after they have some practical experience with their character under their belt. They will uniformly be in a better place to understand the mechanics of what are being offered (which don't always match with the vision the fluff promises) specifically as it applies to a character they have been playing for the last two levels.
Most characters do not get feats at 1st, but get them at 4th. Si if your issue isn't newbie players choosing feats but limited to newbie players playing variant humans picking feats, thats a much narrower slice of cases - ones frankly not needing a broad rule, imo.
Second, the cleric, warlock, sorcerer make up a quarter of the classes- and they all choose their sub-class at 1st. So, if you look at risk of bad first levrl choices - those will likely outnumber the variant human feats.
Again, in my own games, I allow the fntire 1st thru 4th as " intto" and reworking up to 5th.
But, if all this noise about newbie humans somehow turns into a prop for allowing higher level guys to swap out feats/ASI when all is said and done, then it seems... unusual.