There’s some era bias though. A .940 was impossible in the 80s for example, while most of the “all time great” 30+ goal seasons by defensemen came in the 80s.
Both have been shown to be in the realm of possibility within the last 10 years.
I know era's matter - but here are some stats put in a different light.
17x in NHL history a defensemen scored 30 or more goals in an NHL season.
If you expand it to 25+ goals (+/- 5 goals doesn't seem like a huge bar) it happened 43x, including 5x since the turn of the century (2000).
With offensive talented defensemen like Hughes, Makar, Fox and others - I don't think it's a huge stretch to see it happening again soon, and maybe multiple times.
In contrast - 940+ sv% for 50+ games has
never been done in the NHL
The only 2 who got kind of close were Thomas (938 in 2011) and Hasek (937 in 1999). Than you have Price (933 in 2015) and Thomas again (933 in 2009), which aren't that close to 940.
If you expand it to 40+ games, you do have Plante in 1971 who put forth 944 sv%. But no one else, and nothing recent (Bishop in 2019 had 934, in 46 games).
Another way of looking at it. If you tell me a goalie next season will have 940 sv%+ in 50+ games - I'd respond and say "cool, I bet he wins hart/lindsay/vezina, or is a strong finalist minimum".
If you told me a defensemen were to score 30+ goals, I'd say "cool, I wonder if he'll win the Norris"
First one seems like a bigger accomplishment