There's a metric that has been used when talking about adventure gaming. It's an extremely contextually dependent variable, but it's also one of the easiest short hands to qualify 75% of a conversation. So when people say, "we do 5 rooms per hour", there are a few factors that really go into that metric.
How fast is combat resolution?
In my IRL game, running combat for 6 players takes about 90 seconds per combat round. This generally makes most fights last under 5 minutes. The online game is about the same clip, unless there's a technical burp in which we do our best to 'lets just do this and move on'. The OD&D spin-offs I play in aren't much different. The B/X derived game, and the online B/X games, I played in an 80+ session in through Barrowmaze weren't any faster.
How fast is exploration?
The procedures for exploration with the passage of time aren't much different in time to perform procedure. Slowness in games, assuming system familiarity, is more a two-part issue with a DM that doesn't move the game along and players who 'dither', get caught in time traps (I know this statue has to have a secret lever, so let me ask 25 minutes of questions about it) or debate endlessly.
How fast is challenge resolution and time tracking?
Having a cheat sheet/DM screen insert of how long common tasks takes to complete is handy. For instance, Opening a Lock takes 1-4 rounds, the player rolls, the time is ticked off, and then the party moves at an exploration rate and more time is ticked off, then eventually time events happen (usually a random encounter check).
Players get to manage this at a large degree, but only if they are realizing that time matters. So as long as the DM is tracking time well enough, players won't be incentivized to take every single action on every single square inch of the dungeon by running down a check list.
Not all rooms are created equal.
Rooms per hour is kind of an iffy measuring stick too. But it's necessary to a point, as long as you realize that the two room keys, explanation, and resolution will be different for the two below rooms:
In some games, half of the rooms were empty rooms. In others, some have a more complicated scenario presented while others just have X things run out and attack you and there's nothing in the room behind them. If one wanted to truly crank the number, they'd bunch a ton of rooms together, make half of them empty, 3/4 of the remainder would have monsters that would die in 2-3 combat rounds.
The playtest, for example, for Carcass was timed at 90 second combat rounds and 63 out of the 67 rooms being done in 10 hours. There were an average of 4 combat rounds per encounter. That's 6 minute battles. That includes town set up, traveling through hexes on 3 occasions, and the adventure sites themselves.
Hex Exploration has open spaces and safer routes.
When Hex crawling, a lot of travel incidentally reveals terrain. And not every hex is going to have a keyed entry. Many of them will be countryside, possibly a lair for a random encounter, or just a village. Not every hex is going to have an ancient dwarven ruin or giant obelisk with strange markings. Being able to agree as a group on what to investigate and how much to get sidetracked will go a long way to having action packed sessions.
In summary:
A playgroup has control over practicing procedures, time-tracking, and exploration procedures. Rooms per hour is a loaded metric, but its how we differentiate between gaming styles. Those more efficient adventures will show more of the world that is adventured in and explored. This is particularly conducive to worlds that are rich in content and aren't afraid of advancement. Also, I find these much more engaging on both sides of the table. Does CAG own these? No. This is just solid old school gaming that is interesting to the kind of party that enjoys depth.
