You're right...... It's the autopot blokes who can't make up their mind...... When using biotabs, look here a little top watering is OK, with other feeds it's not...... I've never paid any attention to this advise either way, just like the inexplicable advise to dump a drain layer at the bottom of the pots..... But that's just me.
Thing with Autopots is that whatever goes into them stays there, short of taking the pots out and flushing them. And I haven't seem, possibly missed it, any advise to do any flushing from the same blokes. Presumably any salts and other sundry items "building" up elsewhere but the top layer, which supposedly is a prominent feature of the mineral nutes they generally recommend over organics due to possible clogging with organic nutes in the water lines and aquavalves, the danger of aforementioned salts and sundries is probably rather..... Miniscule!