Ironically, the dimensions seem to be the IIHF's impression of what is a standard or acceptable NHL-sized rink, not the NHL's. This article may be paywalled but here's the gist:
https://www.theglobeandmail.com/sports/olympics/article-get-used-to-it-hockey-fans-the-weird-rink-in-milan-may-not-be-going/
For hockey fans who thought the weird rink size at the Milan Cortina Olympics, which is slightly smaller than NHL dimensions, was a one-off – a mistake that won’t be repeated at future Olympics – don’t count on it.
The head of the International Ice Hockey Federation indicated Thursday that even though National Hockey League players have returned to the Olympics, the standard NHL rink may not be coming with them to forthcoming Winter Games.
IIHF president Luc Tardif said he likes the rink in Milan, and shrugged off the fact that the federation uses measurements that are about three feet shorter and a few inches wider than an NHL rink.
Just to recap: An NHL rink is 200 feet long by 85 feet wide. The rink in Milan is 60 metres long by 26 metres wide, or about 196.85 feet long by 85.3 feet wide.
The reason? The International Ice Hockey Federation has a standard footprint, in metric measurements, for what it deems to be a North American-size rink, which is not exactly NHL size.
It’s a close proximity to the imperial measurements used by the NHL, but not exact.
And for Tardif, this is close enough.
The wider rink, known for decades in hockey circles as “Olympic ice” or “The Big Ice” measures 60 metres long by 30 metres wide, or 196.85 feet by 98.4 feet. It is about 13 feet wider than an NHL rink and makes for a much different game.
Sometime after 2018, the IIHF decided to drop the wider ice surface for the Olympics and move to its version of a North American-style footprint, which is used in some arenas in Europe.