Of course they mean something. Goalie performance fluctuates a lot, and there are no guarantees of future performance, but it certainly means a lot more than people blindly pointing to SV% and claiming he's bad and everybody else is good, while ignoring that he played behind some of the worst defensive play in the league last year. There are risks associated with Murray, but there were risks associated with literally every single goalie available this offseason.
I do also find it interesting that many of the people who have been endlessly spouting that playoffs are totally different and everything else is irrelevant... don't seem to place any value on Murray being a two-time cup winner, with the best career playoff results of anybody that was an option.
That isn't proof of anything.