I would be pretty surprised if some form of ability check is not part of the minimum core.
Also, I think he is focusing in that list on action resolution checks. That list (with ability checks) is enough to do action reolution both in a pre-pacakged module and a home-generated game - you're right that the GM for a home-driven game also needs some sort of tools and advice for scenario design (I'm thinking 4e encounter buildng, the Moldvay dungeon tables, etc), but I don't think Mearls is exlcuding that stuff - he just didn't list non-action-resolution mechanics.
"The basic mechanics include movement, combat, ability checks and casting spells." That isn't what Mearls said, though. I would really like to know why, because without them mechanics for interaction with the world outside combat consist solely of spells. I do not consider that reasonable. I would in fact consider it reasonable only if there were no spells with non-combat applications, and all classes were in the same position.