I hope they keep reading here. I avoided the M1 small filter I needed, with slits, as they were almost closed, couple months ago at AZ. Yesterday I looked at the same variant in the ST at WM, slits very opened now. They look like the same filter as M! except the media and adbv.
The issue I now see are the edges of the slits, now that they are punching them through more. I think this could allow more jagged metal edges and that could lead to thin metal pieces going into the after filtered oil stream.
I would prefer nicely punched out holes like the other ones have. Probably the reason they want slits as it involves no punched out material. With slits it is just tearing a hole through, with holes the hole disc must be disposed of.