Agree, PDSs are 99,99 % identical and the only difference is specific gravity of 0.840 at GM against 0.838 at LongTec. Think Castrol Poland did not publish LongTec typical properties because of data available for GM. As for Castrol CIS site, it is not expected to import GM stuff here, so there are no obstacles to indicate them. As you understand any rebadging is quite a delicate action and if GM and LongTec are really identical not only by typical characteristics, but also by their composition, Castrol will never recognize it.
As for Castrol Formula SLX 0W-30, more known as GC at BITOG, I noticed that your PDS indicate 201 C as a Flash Point, but in Russian PDS it was indicated 218 C in 2002, 234 C in 2003 and now this property is removed at all ! Last year I asked Castrol about this discrepancy and what is its real value, but have not got a clear answer. VOAs posted here give quite unstable value too. Would be great to know the reason.