Kiddushin 35a - More on Time-bound Positive Mitzvos

In my sefer, Naiach B'chukecha (see pic on left!), I quoted the Ohr Sameach (Tum'as Tzara'as 11:6) in the context of doing mitzvos in chavilos, where he is mechadesh that this issur doesn't apply to mitzvos that one can do through an agent. At the very end of that section, the Ohr Sameiach writes:

ודע, דכיוצא בזה ביארתי במקום אחר לפי הטעם שכתבו דמשום הכי אשה לא מפקדא על מצות עשה שהז"ג משום דמשועבדת היא לאב או לבעל (דעת האבודרהם), יתכן דדוקא מצות עשה שאין לקיימה ע"י שליח, ולכן חשיב מזוזה ומעקה שבבית שהיא דרה מוכרח להיות מזוזה ומעקה, לכן רק משום שאין הזמן גרמא, אבל מילה ובכורים ושריפת נותר דאפשר ע"י שליח, לא פטרינן לה משום שהזמן גרמא, רק במילה צריך קרא לפוטרה ואכמ"ל

R' Meir Simcha suggests that based on the Abudraham (although he doesn't quote it by name) that the rationale to exempt women from time bound positive mitzvos is that they are tied to serving the father or husband, it would be logical to obligate them in any mitzvah that they can do through a shliach. The rationale of the exemption only applies to mitzvos that they must to themselves, therefore mitzvos that an agent can perform for her, she should be obligated in even when it is time bound.

The rationale of the Abudraham seems strange. If the rationale to exempt women from time bound mitzvos is that she is too busy fulfilling requests from her father and husband, then we should exempt them when the conflict arises. Why would there be a blanket exemption even when there is no present conflict?

It seems to me that there is already a precedent to this idea in the gemara that when a woman needs to be available for other obligations, we have to exempt her across the board and not just in a specific situation of conflict. The gemara 30b, 35a says that regarding fearing one's parent - אשה אין סיפק בידה לעשות שרשות אחרים עליה. Seemingly, this is only an exemption for a woman from kibud av, in a specific situation where there is a conflict with her husbands requests. However, the Shulchan Aruch writes:

אחד האיש ואחד האשה שוין בכבוד ובמורה של אב ואם אלא שהאשה אין בידה לעשות שהיא משועבדת לבעלה, לפיכך היא פטורה מכבוד אב בעודה נשואה

The Shulchan Aruch implies that she is actually exempt from the mitzvah for the duration of her marriage even when there is not conflict so that she will be available to her husband (just that the shach writes that when there is no conflict she is chayeves). This is also meduyak in Rashi. The gemara 35a had a hava amina that since she is bound to her husband, she should completely exempt from kibud av, but concludes that she is chayev. Rashi explains that the hava amina is that even a single girl should be patur, to which the gemara concludes that even a single girl is chayev. Why does Rashi have to explain "לא תתחייב כלל" refers to a single girl? It can just as easily refer to a married woman, but the hava amina is to exempt her even when there is no conflict, and the conclusion is that she is only exempt when there is a conflict. From the fact that Rashi jumps to speak about a single girl implies that a married woman is exempt from kibud av even in when there is no specific conflict like the implication of the Shulchan Aruch.