Li-ion battery max capacity in a bugout situation assumes you always keep them topped off... and if they’re always topped-off for an emergency, well that means you’re probably not using it, not to mention that’s also the fastest way to a kill a Li-ion cell. Best to assume, on average, you only have half the rated capacity.
Solar is getting good these days and there’re panels that output over 1W/oz (actual output on multimeter). These UL solar panels break-even vs powerbanks in ~3-4hrs of stationary, direct, cloudless sunlight... or 1.5-2hrs if you assume the more likely half-capacity battery scenario mentioned above.
For my EDC/GHB, I’ve personally cut my powerbank in half and replaced that 3oz with a 5W (4.5w typical) solar... and mostly use the solar... well, because it’s fun, free/unlimited, and I don’t need to recharge it later.