Can solid offset blocks be used to build a retaining wall in excess of 5'?
There is another and better choice than solid blocks with lips and cinder blocks with rebar. Look at both Keystone and Versa-Lok (versalok.com/products/residential-commercial/standard). These are concrete blocks with heavy fiberglass-epoxy pins which hold the courses together. There are other similar systems now which may be cheaper than Versa-Lok and may be adequate for a wall 4 ft or 5 ft above grade.

Thirty years ago we got a retaining wall built on the downhill side of our lot, wrapping around back until the top of the wall reached grade.  The height is 4 blocks or 32" giving a max height above grade of 28".

The contractor used Keystone "compact units" about 44 lb each. The Keystone blocks are held together with stout fiberglass epoxy pegs and have four holes on top for two pegs (and two holes on the underside) giving a choice of two different offsets per course, about 1" and about 2". This was somewhat overkill for this wall, but it certainly has not shifted. I did not want the possibility of blocks on top ever getting loose and falling on a child or a dog.

I think Versa-lok has some features that make installation easier and result in a very strong and long lasting wall which is easier to build. For example Versa-Lok has slits in the top of each block into which a special gripper is inserted to allow carrying and positioning of the blocks with no need to have fingers in danger.