The newer platy bottles will leak , as they have larger thread than the mini-sawyer.They don't cross thread for some odd reason. I tighten them down and they seem to behave themselves. I use them as squeeze bottles instead of the measly pint bottle that comes with the mini. Much better if your using the platy as a dirty bottle in a gravity feed. The pressure of sqeezing induces more leakage. The mini does not have an independent washer, rather a rubber end cap on the outflow that is not removable. Adding a washer may help to seal the platy bottles, I just make it a little snugger than others.
Not ideal, but takes a little getting use to. You learn to be careful and check for leaks before you get near your clean container. The mini has been a lightweight workhorse for me, after a few decades with the Katadyn Pro. If you find better dirty bottles, please let it be known.
https://www.youtube.com/watch?v=a2-RiE3yMjg
A few minutes into this video he attaches a 2l platy and you'll see what happens.