Why does “בני ישראל” sometimes include גרים and sometimes not?

Question

Tosafos (to Suka 28, Sanhedrin 86, and M'nachos 61; and Tos'fos Harosh to Sanhedrin 86) cite various verses containing the words "בני ישראל", b'ne Yisrael. In some cases, they note, the g'mara seeks an additional d'rasha to include converts into the halacha that the verse assigns explicitly to b'ne Yisrael. In others, the g'mara does not seek any such additional d'rasha. They ask this as a contradiction: if such a d'rasha is necessary, why is it not necessary everywhere?

They reply (in all three places, as do the Tos'fos Harosh in Sanhedrin) that "maybe" there is some such d'rasha that the g'mara does not mention.

Does anyone (1) know of a stronger version of that answer, one that either (a) explains why such a d'rasha would be mentioned explicitly in some cases and not in others or (b) lists such d'rashos that the g'mara does not, or at the very least (c) claims the existence of such d'rashos without qualifying that claim with "maybe"; or (2) know of another answer to Tosafos' question?

Answer 1

Malbim (to Lev. 4:2, sec. 191) argues for your option 1c: there are derashos in Sifra for all three of the cases that Tosafos mentions - being a zav/zavah, pledging erachin and performing semichah - that converts are included.

He explains at some length that indeed "bnei Yisrael" includes only born Jews. So mitzvos fall into several categories:

1. Those where it doesn't say anything about "bnei Yisrael." Those indeed apply equally to all Jews, by inference from the statement, "One Torah shall be for the native-born and for the convert" (Ex. 12:49).

2. Those where it says "bnei Yisrael," and there is an explicit or inferred statement that includes converts.

3. Those where there is no such statement, and indeed converts are excluded.