Hydraulic Lifter Question

Engine has been sitting for a week or two.

When doing a valve adjustment, I noticed some lifters are completely solid and others move a few millimeters. (But that is all, maybe 4mm).

I removed the "squishy" lifters, submerged them in oil and pumped them up and down, but they never get rock solid. These are new Ford lifters.

Is this normal?

I am trying to diagnose my vacuum gauge needle fluctuation issue accompanied by a rough idle. You can watch the youtube video on it here:

Also, aren't hydraulic lifters supposed to bleed down completely over time? As in you can compress them by hand?

How far does a lifter compress anyways?