Can't really go wrong either way. Some still link HM oil to the old days of "seal swellers" additives that would stop a car from leaking for a while as long as you kept using the seal sweller. The moment you stopped using it the seals would retract and leak even more than before you started.
Not necessarily "the moment", it can take a while for the seals to shrink again, even many miles, so people who flip back and forth, don't see the direct correlation between their premature seal wear and the HM oil.
Modern HM oil don't do that. (according to the manufacturers)
This is a false statement without a qualifier of which manufacturer you're talking about. Valvoline Maxlife for example, does in fact do this according to representatives.
These are seal conditioners which prevent the seals from getting hard and shrinking in the first place. Sort of like armor all for your seals. (No Armorall flame wars please, replace with your favorite rubber protectant if you will)
Show us a statement that they work like armor all instead of like a seal sweller. That's not even how the are marketed, if they had only benefits they would be called "advanced protection" rather than "high mileage".
There is no conditioner for seals that can keep them from aging. Conditioner is marketing department doubletalk because seal sweller can be a dirty pair of words, as they have seen from public discussion. It is a deliberately vague, non-specific word that does not mean it's like armor all.