An interesting thought, Bro. Epley, and one I hadn't considered before. I have no idea whether this episode in the PAOC was affected in any way by the type of racial issues that affected other organizations of the day (and which included some of the same men, such as Goss). But I'll hasten to add that I've come across no indication of it.
In any case, it does seem that other factors, besides McAlister's apparent reversal on the Godhead, were at play in changing the course of the PAOC. One likely suspect is the eternal security doctrine, which had gained significant traction, primarily in western Canada, through the influence of Small (and William Booth-Clibborn), but was at odds with the views of most other PAOC leaders.
When the conference vote to affiliate with the AG passed, it was by a majority of "about two," with about 17 members in attendance, according to Small. Had there been a sudden mass defection from the Oneness position among these men, the outcome of the vote would be understandable, but such was not the case.
It is still a puzzle to the writer how some of these brethren swung the way they did so abruptly, as he had had personal conversations with some regarding the vital question of the Godhead, and baptism in His name. These were even more radical at that time than the writer, therefore we cannot reconcile the abrupt turning without some statement of facts why [Small, "Historical and Valedictory Account...," p 2].
Based on opposition received on other occasions to his "eternal life" message, Small "wondered if this was not the pivotal point that swung the whole project in the way it went."
Significantly, Small at the time also held credentials with the PAW, so it would seem that the PAW was not making an issue over his position on eternal security.
I'm kinda winging it here, but if I'm not mistaken, the AG by that time had already taken a stand against eternal security.