Maybe the leveling plug is post fluid filter? That would be my guess as to why the manual says to fill from the breather. BTW, like someone else said in this thread, the proper way to fill from the breather tube is to remove the entire rubber tube via the spring hose clamps. There's a small disc...
I just drained and refilled my 2023 XLT. Something that I see being done incorrectly in all the YT videos and stated in other comments in forums concerning the filler tube. You're supposed to remove the entire breather tube per the 2022 Maverick service manual that is posted elsewhere on this...