Most all AR handguards will move a tad if enough pressure is applied. Clearance between HG stop cast in A-1 HG and diameter between teeth on barrel nut. Stop diameter is mfg a tad smaller. Nature of design. Usually very minimal and un-noticed unless one actually tries to move them. Over time and with use the plastic stop will wear increasing clearance and movement (scale of hardness, plastic vs metal, metal wins).
There are many reasons why the original ergonamic A-1 HG's were replaced with the A-2 design but mostly due to being more prone to breakage. As HG end cap loosens over time with use and plastic wears a tad, a little movement can occur on the business end also. Doesn't effect much in milspec shooting performance (2-4" at 100yds) but there is a reason a competition rifle has free float HG's. They remove the stresses (harmonics) from original design and can increase accuracy in most instances.
Slip ring also has clearance between notch and gas tube and is made to actually move, same with snap ring. Without clearance it sure would be hard to install a barrel but barrel nut shouldn't move once tightened and fail safe if it does is the gas tube holding / locking it. Shoot it and have fun.