I would expect that double size but half the number of combats is too easy for many groups. The daily resource classes will do better with condensed combats. Their AoE can hit more, one casting of a buff can last for multiple encounter budgets worth of foes, etc.
The increased XP budgets allow for larger foes, as well as more of them. Also you're assuming that the players
took AOE.
Yes, a reduced number of encounters increases the effectiveness of long-rest classes. But that's assuming these are combat specialized PCs who have little capability for doing anything outside of combat. Long-rest classes can't trade out their spells on a short rest and they have a cap on their total spells known, there are plenty of things that do not require the complexity or investment of combat that you can throw at players to take advantage of this. If you do, the end result is that PCs become
less specialized and more utility which overall reduces their spotlight-stealing during combat.
Drop a couple magic items and say "okay, now who's got Identify?"
I probably run 6-8 "encounters" per session. That can cover days, weeks or even more of game time. Probably 2-4 of those are combat encounters. The parties in my game have a lot of control over how they approach encounters and I'm not a huge fan of dungeon crawling. The rest consist of various world hazards, traps, threats and other things which are quick to resolve and rarely threaten the party, but present challenges outside the combat pillar. They may require party resources, but it will typically NOT drain HP or class features. My combat encounters tend to be large one-shots such as a single powerful monster and several lesser monsters aiding it in addition to terrain and other dangers; or larger "running" encounters think: LOTR the escape from Moria where the party doesn't have a chance to rest and everyone is reasonably ran ragged by the end of the fight.
I don't think I could reasonable run 6-8
combat encounters per session. I just don't think I have the energy to throw a half-dozen fights against readily defeatable foes for no purpose other than to drain their resources. If I want to drain their resources over time, I just limit the types of rest they can get. Getting a "breather" may be the best thing you can get today. You may even have to fight with a point of exhaustion tomorrow.