Yes it is. However, I think you missed one as well. You may use a retreat to get units through enemy lines and consolidate your forces.
For instance, if Russia has 8 Infantry, 3 Tanks in Persia and 24 Infantry, 9 Tanks and 2 Fighters in Russia, you can attack the Germans in Caucasus with everything and retreat everything to Russia where you can be a pain in Germany’s side.
Does not always come in handy, but there are times it is useful. Namely in the above situation, but also when you put a Submarine in SZ 2 and your British fleet in SZ 4 then attack the German fleet in SZ 3 and retreat your entire navy to SZ 2.