Anybody who has been military aircrew knows that this is part of the game.
You fly over somebody else's territory, no matter how briefly, you get in the poo (friendly nation) or risk getting shot down (unfriendly nation)
The Russians have done it, the Americans have done it, the Turks have done it, The Syrians have done it, the Greeks have done it, the Isrealis have done it, and I'm sure we have done it.
I have no doubt that in Russian military headquarters there are some pragmatic conversations going on about it.
It is part of the game. Pushing limits to see who is weak and who has a pair. It may seem childish, but the reality of international geopolitics generally is.
In the last few years, the Syrians have shot down a Turk. The Turks have shot down Syrians. It is a hot war zone.
We all know.
You don't cross the line, and if you do, then beware.
p.s. The whole "which side of the line were they when hit?" discussion is just cr@p. What do you think this is? Tag in the playground?