My main planned use of shared pots, should it support the function, is for my wife and I’s joint spend, not bills, but regular monthly spend. We have our own money but then have jars at home with cash in for various things like gifts for upcoming birthdays, clothes for our daughter, food shopping but only the person who has the cash can use it.
A shared food shopping pot where each of us has access would mean whoever was in the most convenient position to go shopping (on the way home from work, on lunch etc) would have access to the correct funds instead of needing to collect the cash from home first.
Other solutions we have tried have been to do it on a credit card we both have, but this depended on our discipline and admins skills not to go over budget. A shared pot would act the same as our cash bag where we can see exactly how much is left.
My opinion on security and who can withdraw is that you shouldn’t want to set something like this up with somebody you don’t trust anyway. While any manageable features that improve security are obviously welcome, it should only be assisted where possible by monzo, the security around who you choose to give access to your cash should lie on your own shoulders. That’s where i think the gift collection is a bad example of where shared pots would be useful