BST soloing NMs often doesn't have the luxury of just calling another pet. If the NM is deadly enough, you're lucky to get pet food keeping it alive long enough to outlast call beast retimer.
And if you want to spend a day of doing intensive events like that, it's ridiculous to need to fill so many inventory slots for basic functionality like that. If you're having no issues, you aren't fighting hard enough targets.
This problem is akin to a ninja needing to fill all their inventories just to go out for a few hours and fight/tank hard NMs while only using their own spells and JA. SE would never allow that imbalance and yet here we are, with BST.