An 11in SA58 is made for storage/ handling in tight places...bodyguard work, aircrew personal weapons, armored vehicle crews etc... Those that have need of a heavy hitting weapon with penetration, but dont have room for a longer or more cumbersome version. The trade off
Is increased blast/ flash over the full size models. The same applies to 5.56 guns as well, a 10.5 inch Colt Commando is nothing short of rude lol and will drownd out the guy shooting a full size Fal, or M14 next to him( picture .300 win mag full auto) 11in 7.62NATO guns are worse! Cool factor is high, but ear plugs WITH muffs is the normal way to shoot it.
Aside from the SBR tax stamp required on the 11", the 16" and longer is just more practical for most uses. I've owned a FN 50.63 para, and 50.00 full size metric, and two L1A1 inch pattern over the years.
Probley the best comprimise is a 21"
Folder like a lot of countries used.