The Chizkuni says that a Ger shouldn’t really eat the Korban Pesach, since his forefathers didn’t experience being saved by Makkas B'choros. Yet, since he wants to be part of everything, he is just as good as the native born FFB Jew and he eats a Korban Pesach alongside. But the: בֶן נֵכָר יב מג “stranger” who is a Yid: שֶנִתְנַכְרוּ מַעֲשָיו who became a Rasha and doesn’t want to be part of it, can indeed draw himself away, and: וְאִלוּ הָיָה שָם לֹא הָיָה נִגְאָל no Korban Pesach for him.
We see how everything goes according to your opinion and desires, independent of whether you were truly involved. Similarly, it says: וַיֵלְכוּ וַיַעֲשוּ יב כח the Yidden immediately went and did (even though they had not yet done anything) since as soon as they wish to do, it’s as if they did. (Rashi). The בְכור הַשְבִי firstborn in captivity also died, although they did not do anything to hurt the Bnei Yisroel, since they were happy with our Tzaros, so they are just like a Mitzri, and his Bechor dies also. (Rashi). Notice how this Parsha is especially loaded with the Ikar Ikarim of: רַחְמָנָא לִיבָא בָעֵי Hashem wants our intentions.
