Wouldn't it make sense that the FA20* would fit in the same space as the EJ20/EJ25*? The FA20F specifically is a 2015+ WRX engine, right? And the 2015+ STI, which uses the EJ257, uses the same body and chassis that the WRX uses, so it would make sense it would physically fit.
Also, https://www.carthrottle.com/post/this-300bhp-wrxengined-brz-is-the-car-we-wish-subaru-would-make/