It will pose enormous problems, because buyers buy with an understanding that the delivery date range is meaningful and sometimes they are relying on things to arrive roughly on time.
Basically, if you're a seller and you see a message like this, it doesn't matter what your handling time is, you better get that item into the post by 22/23rd May.
Yes, ebay has a lot to answer for, I would have expected better, even if it is an automated system that calculates the dates. It shouldn't be that hard for them to formulate a program that won't estimate a delivery that is before the 'send by' date.
PS I wouldn't take their word for it that it won't affect your account if things are 'late'.
