Yes, I’m aware of this; here GitHub - wwmm/easyeffects at pulseaudio-legacy is stated the following:
This is the old PulseEffects version supporting plain PulseAudio server, not Pipewire. This branch is in maintenance mode and no longer under development.
And again in the link which you posted:
Once the PipeWire branch is ready it will be moved to master and a legacy branch will be created with the current code targeting Pulseaudio. But I have no intention to work on it after moving to PipeWire. Maybe a bugfix for some issue that is really serious.
However, by searching around, PipeWire is not yet a complete replacement of PulseAudio, and maybe (this specific case is certainly related to the developer decisions) pulseaudio-legacy will exists until the day that PipeWire wil become a complete replacement.
Also maybe someone else coult fork it and continue to its development.
Who knows…
Anyway: for avoiding confusion, imho, the developer could change the name to PipeEffects…