Maybe part of the reason people don't think <6ft goalies are underrated is that Saros is brought up as an example of excellent <6ft goalies in the league, despite having a grand total of one Vezina finalist finish to his name since he was drafted almost 12 years ago.
Because there is systemic bias against shorter goalies. In the past 20 years a sub 6' goalie has won a Vezina/Smythe 5x with Quick/Thomas having 2 of the highest peaks of any goalies ever. During that same time frame a 6'5+ goalie has won a Vezina/Smythe 1x, despite there being infinitely more 6'5 goalies drafted/playing in the NHL. Goalies over 6'5 are seen as a great asset, yet looking at the results that height of goalies (and abundance of them too) has produced in the past 20 years, it is far worse than a sub 6' goalie.
It is literally equal with 6'4 goalies and above (5 to 5), yet if you asked scouts/coaches "knowing nothing about groups of goalies, would you suspect 6'4 goalies do better/the same/worse than sub 6' goalies?" Do you think anyone would take the sub 6' goalies?
If you have a talented goalie who is tall, that's great, but height isn't anything to overly fawn about and if you see a talented goalie even sub 6', they are 100% worth a shot. The real problem the way I see it is the amount of atrocious goalies who have gotten a shot because they are 6'4+, meanwhile looking at the results of sub 6', it's astonishing considering how few of them there are.
Even using the biggest outlier I can find, it's astonishing that at 5'5 Darren Pang posted the 8th best save percentage in the league over a season. Even when he fell off the following year, he still wasn't the worst in the league like you'd expect someone as short as him to be (on a terrible team too).