Ambiguity in the Rambam: What Types of בָּא Are Covered by the Term?

Question

This is a follow-up to my previous two questions:

Within the following excerpt, does the term בָּא (which occurs thrice: twice with one meaning, and once with another), include all possible types of intercourse and intimacy, or just some ? If so, then which, exactly? And if some are to be excluded, then what would those be, specifically?

אֲבָל יִשְׂרָאֵל הַבָּא עַל הַכּוּתִית בֵּין קְטַנָּה בַּת שָׁלֹשׁ שָׁנִים וְיוֹם אֶחָד בֵּין גְּדוֹלָה בֵּין פְּנוּיָה בֵּין אֵשֶׁת אִישׁ וַאֲפִלּוּ הָיָה קָטָן בֶּן תֵּשַׁע שָׁנִים וְיוֹם אֶחָד כֵּיוָן שֶׁבָּא עַל הַכּוּתִית בְּזָדוֹן הֲרֵי זוֹ נֶהֱרֶגֶת מִפְּנֵי שֶׁבָּא לְיִשְׂרָאֵל תַּקָּלָה עַל יָדֶיהָ כִּבְהֵמָה

My previous two questions dealt mainly with linguistic matters; this one, on the other hand, is primarily concerned with context and authorial intent.

Could someone well-versed with the Rambam's work in general, or the Mishneh Torah in particular, help clarify the issue?

Answer 1

I would think that the parameters of "coming upon" here is the same as in other cases, where both partners in the act are Jewish. Those are spelled out in Chapter 1 Halachos 10-12.

Answer 2

It is very hard to tell as most commentators struggle to find the source for Rambam's ruling to start with. Normally Rambam's rulings are based on known Talmudic passages, which shed light on the Rambam's opinion. In this case, the commentators struggle to find a source that stands up to scrutiny, which makes it difficult to get to the Rambam's intent. This is also presumably why the later halachic authorities do not mention this ruling of Rambam.