l'asuyay basar v'dagim u'beitzim

The mishna in nidda 50a says that not everything that is metamey tumas ochlin is chayav b'maasros. The gemara explains that this includes 3 things: meat, fish and eggs. The Tosafos Yom Tov asks three questions on this:
1. The gemara lower down on the page quotes the mishna in maasros that says that mushrooms are not chayav in maasros so why isn't that listed?
2. The Rav M'Barenura explains that these things are excluded because they're not gidulei karka but in the first perek of maaser sheni, it says that cattle is included in gidulei karka.
3. There are some other foods - "pagim boker v'kafnios" which are peturim from maaser so why aren't they listed here?

Tosafos Yom Tov says that when the gemara says "l'asuyay basar v'dagim u'beitzim," it means that even though these things are "ochlim chashuvim" they are still not chayav in maaser because they are not similar to dagan, tirosh v'yitzhar. In other words, there are definitely other foods that may not be chayav in maaser but there are no other ochlim chashuvim.

The Ritva asks another question: Basar is chayav in maaser beheima so why is it included in the list of foods that are not chayav in maaser? He says that it's just referring to basar chaya. He says that was actually the girsa of the Rabeinu Chananel.

I would answer the questions of the Tosafos Yom Tov that the gemara isn't attempting to give an exhaustive list but just a simple list that it doesn't have to qualify in any way. It's not going to list a couple of vegetables unless it's true across the board for vegetables. I would then answer the basar question that either the gemara understood the mishna to be referring only to maaser dagan and not maaser beheima or that when "basar" isn't chayav in maaser beheima, the animals are.

The Rashash quotes the Tosafos Yom Tov and gives an explanation but I don't completely understand it.