That part is geographically accurate actually, according to the link here to the current top post on this sub.

https://www.reddit.com/r/boston/comments/zngjd6/geographically_accurate_boston_subway_t_map/?utm_source=share&utm_medium=ios_app&utm_name=iossmf

To respond to your point about opposition from the locals at Savin Hill, on the one hand I feel like I missed an opportunity to have the yellow and dark purple lines meet at JFK. On the other hand though, this will either a) never happen or b) be implemented by a god-emperor who doesn’t care what the locals say.