From what we heard so far...it doesn't seem as though Series X's SSD will be difficult to work around at all. It's just that the PS5's SSD is just faster, not that the Series X is not up to par and difficult to work it. No different than developers will "work around" the weaker CPU and GPU of PS5 compared to Series X. Again, the CPU and GPU of PS5 isn't bad or not up to par, but I think it's pointless to say something like that if your SSD is still strong regardless of a stronger one available.
Of course 3rd parties will release games that work on XSX SSD, they will mostly even make games that work on PC with similar RAM but HDD. And sure the system isn't hard to develop to, but with a significant difference in the I/O compromisses will be made. The place where we will really see a possible change in game design is exclusives.
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"
Azzanation: "PS5 wouldn't sold out at launch without scalpers."