You keep mentioning customers who purchased at the regular price. Ok, then let’s call them “A”.
Then you have customers who purchased at a discount and know how to exploit the system. Let’s call them “B”.
And then there are customers who purchased at a discount but didn’t even know that there was a system that could be exploited, so let’s call them “C”.
I understand that A have priority of taking the advantage of grace periods. But what about B? They didn’t pay the full price. Your argument suggests that A should have an advantage over C, and it’s understanable, since A contributes the most, financially, to the company. So how is B allowed get away with it by saving 100 euros, when they, just like C, only paid a discounted price for the product and not full price like A? The only difference between B and C, is that B knew a few tricks and C didn’t.