It sounds odd, but it makes sense considering recording Raw, then changing the staging, then recording WrestleMania, only to change the staging back to Raw would be a monumental waste of time.
As WWE works its way through providing programming for fans while the outbreak of the COVID-19 virus overtakes pretty much everything else, the company is trying to find the most feasible and financially viable ways of putting on their shows. Pre-recording everything over the next two weeks was ultimately the solution.
That means, on a closed set, WWE is going to hammer out all tapings for every major show, including WrestleMania 36 and then edit the snot out of the programs to make them as entertaining as possible. Like the way Hollywood Studios will shoot a film out of sequence, this also saves on the cost of flying Superstars to the PC, which in and of itself has become a challenge.
Because WWE is also allowed to have no more than 50 people on a closed set at any one time, this makes sense logistically too. Per reports, the next two episodes of SmackDown and 205 Live were taped on Saturday. Today (Sunday, March 22, 2020) the next two episodes of NXT will be taped. Then, on Monday, Raw will reportedly air live from the PC and WWE will then start taping all angles involving Raw Superstars over the next couple of weeks.
Further reports are that on Wednesday and Thursday, WWE will begin shooting WrestleMania. The way the scheduling works, the post-WrestleMania Raw will actually be shot before the WrestleMania PPV itself.
The only risk here is that spoilers sneak out and the Internet has a field day with the results of that Raw episode, thus spoiling the results of WrestleMania. If WWE is at all worried about that, they might want to shoot two possible outcomes, just to throw fans off their trail.