The Mishna on 19b begins a discussion about שן. It then discusses eating כסות או כלים and says the chiyuv is only 1/2 nezek, as Rashi explains - due to the fact that this is meshune. Does this automatically mean we have jumped to keren? Perhaps not. My Rebbe, Rav Lichtenstein שליט"א points out that the Rambam brings this halacha in perek 3 of hilchos nizkei mammon, which discusses nizkei shein. If it were really supposed to be keren, then it would have made sense for this to be elsewhere in the Rambam's discussion of halachos related to keren.
This raises a possibility that meshune is a general din, not necessarily related to keren per se but any av. This would work well with the first mishna in the second perek as well which changes from regular regel to mevaetes (see tosfos there who says we did jump to keren but it is brought here since the din is parallel). There is one problem though with applying meshune to regel since they seem to be contradictory as the definition of regel is normative - היזיקו מצוי. Rav Lichtenstein suggested that the בעיטה that is meshune is in the context of a normal action of walking, as opposed to בעיטה we saw earlier that is pure keren -- in mishna 15b.
This solves another problem in that we we have been seeing
two different chiyuvim of keren: כוונתו להזיק and משונה and they dont
necessarily go together. So, we would now say that only כוונתו להזיק is
keren. Of course we need to work this out with the issue if petur reshus harabim as well.