indeed I've test on one of my site with app restriction and there are a few (very few, as 10 packets in several days) psiphon blocked connections. Same, on this site I'm sure noone has installed that on purpose.
I use Sophos XG in my company. Some users pass Sophos Web filter and Application Control with psiphon proxy 3 app. I create new rule Application Controll --> Deny All and Web Filter --> Default all block but psiphon proxy connecting. This is a big big so big problem. Soon all users begin use this program :)
TAC sent me IPS signature FOS 5.2.10 (flen-520-3.0406.pkg) few days back, i thought I was able to blocked psiphon completely but after a few minutes of waiting, psiphon successfully connected. whew!i started to scratched my head again ;)
Hi. I think we are in the same country and I know what you want to achieve. Well, I guess you already know a lot about this, but in my opinion you are using too much resources to achieve it (I guess including your phone for psiphon). It is up to you, but if I may suggest you could use another method such as wireguard in the router. For me, I only need 4G modem and this AR300M for all devices to have internet at good speed, without need of proxy setup, and very much stable.