A couple people have already mentioned that Summoner and Scholar are the exception to having separate stat allocations. The reason that's the case is part of the way classes differ from jobs, so that may be worth a little explanation.

Jobs are an advanced and specialized version of their primary base class. They retain all the skills and traits of their base class (though in a few cases, the effect of some of those skills may change). They use the same XP/Level as their base class. And they use the same stat allotments of their base class. Essentially, a White Mage is still a type of Conjurer, a Dragoon is still a type of Lancer, etc.

In most cases, like a Gladiator (class) becoming a Paladin (job), or a Thaumaturge (class) becoming a Black Mage (job), they also continue filling the same role in groups and essentially doing the same things they had been. They're simply better at it by having the advanced job. That keeps the stat point allocation pretty straightforward.

Arcanists, however, can advance/specialize into two different jobs, Summoner and Scholar. A Summoner is a type of Arcanist, and a Scholar is also a type of Arcanist, so they both use the Arcanist class's stat allocations. The issue is that while both the base Arcanist class and its Summoner job fill a Direct Damage role in groups, specializing in Intelligence-based magical damage, its Scholar job specializes in Mind-based healing. So if you're going to use both of its jobs you need to decide how to allocate its stats to work for both of them. (Some people do that by simply dividing ACN stat points half to Int and half to Mnd. Others do it by focusing on one of the two jobs for a while, then paying for a stat re-allocation, then focusing on the other job for a while.)