Especially to put what it is actually called in parenthesis as if everyone calls subtractive synthesis "Eastcoast".
This is certainly something very specific to the path you took with synths.
East Coast synthesis, often associated with subtractive synthesis, emphasizes traditional keyboard performance, harmonic richness, and filters to shape sound. Meanwhile, West Coast synthesis (credited to Buchla) leans more experimental, focusing on waveshaping, FM synthesis, and unconventional control interfaces.
The terms themselves have been around for decades and have become shorthand to describe these philosophies of synthesis design and architecture of synths. You might not hear them as much outside modular or academic circles, but they’re far from obscure.