Membership Fixed period, wrong start date
Yes this is an aspect of / issue with Rollover - ie when someone signs up, civimember effectively gives them the start date of the membership cycle on the day they sign up, and then adds on the extra year. so yes seeing 'start date' of 1 May 2018 for someone signing up on 5 March 2019 fits with the civimember logic.

i don't say i necessarily like what it does but the logic is consistent but means that you may need to pay more attention to the Join Date than the Start Date.

That is, assuming everything else looked right, ie End Date was 30 April 2020