I can accept the not stacking of Dawn Mulsum, but I don't get the issue with having pet food synthesize and stack to 99. Beastmaster is still limited to the Reward timer, so it's not as though more food in your bag increases your pet durability by default. It's convenience and courtesy to current inventory issues.
Whenever the development team associate inventory space as a form of difficulty to battle mechanics for a job, I cringe. If I wanted to utilize Beastmaster's Monster Correlation properly. I'd be carrying 7 stacks of jugs (Beast, Plantoid, Lizard, Vermin, Bird, Aquan and Amorph), 1-2 stacks of pet food, possibly some dawn mulsum, and a stack of pet roborant if I wanted to clear a bunch of status ailments that using augmented Reward won't remove.
Beastmaster is currently the most expensive consumable job, even with Bestial Loyalty. It doesn't matter that Ninjutsu/Ranged Attacks work differently and are used at a faster rate. Beastmaster might not use consumables as quickly but it still adds up fast in cost and requires significantly inventory space.
Other consumable job cost & inventory benefits:
Pouched items
Recycle/Ninja Tool Expertise/Scavenge
Universal Ninja Tools/Trump Card
Beastmaster:
Bestial Loyalty (20 minute timer)