No, I have closely followed the development of Polish jazz since 1973, with visits to Poland and gigs in Germany. I also met some of the musicians mentioned in the jam session later ...
On my shelf - a 'Who's Who' of Polish jazz ...
All Stars After Hours: Night Jam Session In Warsaw 1973. Polskie Nagrania Muza SXL 1033 [1973]
See: https://www.discogs.com/de/release/5982337-All-Stars-After-Hours-Night-Jam-Session-In-Warsaw-1973
Oh yes - the Oles Brothers! I have listened to this impressive concert at Od Nowa Jazz Club in Toruń:
Custom Trio & Andrzej Przybielski: Free Bop. Polonia Records POLONIA CD 226 [2000]