As a Melee weapon the shovel is too slow and has such a short range that makes it unusable. As a digging tool the capture points are usually inside buildings, so you don’t really need to build trenches or dig foxholes. Either they put the point in the middle of the desert and give us time to build defences or it will continue to be a useless feature
Historically in Stalingrad the Spade was often used as a close Combate weapon, they were sharpened the handle shortened and used to great effect, apparently you take of a man’s head with one pretty easily if you came up under the chin.
Other than that specific campaign/battle I have not read of them being used though in that role to any extant