D&D 5e is not balanced around a 6-8 encounter, 2 SR day.

[PhoenixPhyre]

No arguments here - but I suspect the one encounter per long rest table is far more common than the 6-8 encounter per long rest table.

I'd add to that that it is a balance problem that should have come out in playtesting.

Honestly, 1 encounter per long rest goes against the entire design of the game. It's a "don't do this" case, because otherwise you have to rewrite everything. And systems that handle 1 encounter per long rest as a default gracefully don't usually also handle N encounters/long rest. The 5-minute working day was a huge issue in 3e as well, which didn't have the LR/SR distinction. And 4e was designed around more than one encounter per day--otherwise the "daily/encounter" distinction (and healing surges to a degree) break down.

And you can do 1 encounter per LR as long as it's not the default. Balance is over the whole campaign (or arc), not over individual days.