The company that sells the power bank is, at best, focused on a balance between you having a good experience with them, and you not dying and suing them.
If you charge the pack, it's more likely to have power which is why you bought it. Depending on how long it sat on the shelf, it may not have power. If you charge it, you are less likely to go online and write "I bought this power bank and it can't power anything!".
You getting the most satisfaction with it is in your hands. Charging it to a profile that gives you what you are after in return for the effort you are willing to make is most likely to give you your own satisfaction.
In some of the threads I read that mention charging short of full to increase the life of Li batteries, they also mention that unless it's sometimes charged to 100%, the BMS may not be able to keep the cells balanced. From that, it seems as if there is good reason for both, and striking a balance between them. What that best balance is, I'm still reading/trying/riding, etc. My picture will change.