Id suspect a ring alignment issue or perhaps a measuring error or at worst a cylinder that should have bored to an oversize

Not likely a machinist would miss that

Assuming the engine was bored and not just reringed

Run the engine for a few hours

Recheck compression. Hot.

then dump a teaspoon of oil into each jug and measure again

What exactly was done on the rebuild is the question

It takes some experience to determine how far you should go

Rebuilding on budget is always difficult