So a point of clarification: Controlled sidings actually have slightly different rules than other main tracks. With main track, trains can't clear up at hand operated switches if the TT speed exceeds 20 mph and there is no electric lock at that switch. On a controlled siding, provided there are no intermediate signals within the siding, trains can clear up at hand thrown switches with no electric locks as long as the maximum speed isn't over 30 mph (Rockingham Junction is a good example of this, with the passing track being a hand thrown switch off the controlled siding, and TT speed not exceeding 30 mph). For the most part we still primarily use #1/#2 instead single tk, and controlled sidings.
Of course, if there is an electric lock then it doesn't matter, but both Pan Am and Keolis generally limited controlled sidings to 30 for this reason so they don't need to install electric locks.
As far as track speeds, 25 isn't awful when it's on welded rail. 40 is better, but 25 is still a lot better than 10. On jointed rail, doing 25 can make for an eventful ride over some of the track on District 1, but for what it's worth, in most of those spots, 10 still causes you to lurch and rock, it's just not as obvious. Mentally 10 is pretty exhausting though, especially in the middle of the night, or in areas where there's literally nothing to see, like east of Waterville.