I can use flight connections (and bypass a security check) despite the Dublin Airport website stating self connecting passenger can't use flight connections?
Also is flight connections T2 to T1 actually faster than exiting T2 to landslide and entering T1 airside through fast track security?
Yes to both. T2 is just a bolt on to the side of T1. Bit of a walk but better than going landside. The "no self connecting passenger" thing is a bit of a mystery, you are correct it says this, and is repeated in Aer Lingus' paperwork too, but I can't see how it can be enforced. Not least because it would require quite a delve into multiple systems to work out if it was a connection or self-connection.