I cant speak to their training but they for the large part operate like a typical army i.e large vehicles large units fighting for strategic checkpoints on the main road and major towns.Then haven't SNA been trained to operate like insurgents? One would assume that, since AS have been the no.1 enemy of the Somalia for the past decade+, all types of training would be to accustom them to the given circumstances and thus defeat AS.
Also, the number of Liyuu exceeds the total number of all Somali federal forces by at least the double. Liyuu was established around the time when AS started fighting against Somalia. With that said, there're simply other factors playing important roles that's emboldening/strengthening AS.
You dont see units of 5 SNA walking into their rural villages or videos of small troops camping in far off road places to maintain pressure on their enemys safezones.