What is your opinion on the wording of “the magic action” and spells AND features that take longer than one round to cast? See my original post on the matter
I saw that. It would apply if, for example, someone was casting Find Familiar as a spell.
They need to take the Magic action to cast it (because that's how you cast spells).
Because the casting time is 60 minutes, they are occupied the entire time (have to keep using their actions to keep "casting" it) during that time.
But ... here, the spell's description states what the casting time is. ("Most spells require the Magic action to cast, but some spells require a Bonus Action, a Reaction, or 1 minute or more. A spell's Casting Time entry specifies which of those is required.")
Except the Familiar Pact provides a different casting time. ("and can cast it as a Magic action").
So the spell's casting time entry specifies that the spell requires "1 minute or more." But the Familiar Pact changes that to "require the Magic action to cast{.}"
IMO, YMMV, etc.
(I don't like it, but I think that's the rule.)