Seeing as how you are in the Model Y forum, you will get answers pertaining to Model Y since most of us don’t own M3. You should ask this question in the M3 forum.
Or, remove your driver side wiper arm and find a MY and lay yours over the top to see if it is the same size. As the windshields are different sizes I would imagine the dimensions and design are different or they would be the same part number. No reason for Tesla to have two different parts if they work interchangeably. Just looking at the drawings in the catalog they are definitely shaped differently. MY appears longer to account for taller windshield (look at the right blade tip relative to the arm and hinge). MY also appears flatter whereas the M3 appears to surge away from the windshield at the spline (probably to clear part of the mechanism).
M3
View attachment 769831
MY
View attachment 769830
I think your best bet is to buy a MY wiper arm, then disassemble the middle spray nozzle and attach it to your M3 wiper arm, cutting the tubing to fit in between.