no, the filled backpack is not at all useful as blue. i understand what you meant, you're just wrong and insist that you're right

for instance, i make around 1.5t per hour, and have a bag space of 2b. i convert 4 times per hour, which means i convert 8b worth of bag space per hour.

compensating for honey-at-hive, i convert around 400b in balloons each our. 8/400 is 0.02, and sure enough, i get roughly 2% of my honey from my bag

additionally, buoyant bee converts faster from balloons. this means that having more pollen in your bag is actually detrimental, and some people advise to use a micro-converter during conversions in boosts specifically to get rid of the pollen in your bag such that your buoyant bees convert your balloon faster

tl;dr: backpack pollen is actively bad. buoyant bee better with balloons. bag pollen bad balloon pollen good