Having Sneak Attack, Phalanx and Rogue in the same bucket, and Phalanx not in the Fighter bucket, is something I will have to wrap my mind around![]()
I think you are right to be confused, but perhaps not for the reason you think.

D&D has always had problems with phalanx fighting (can't speak for 2e, but certainly in other editions). It's just never been possible (a) to hold a spear and a shield and fight efficiently, and (b) to fight better when someone else beside you is doing the same. It shouldn't be a tough thing to design, but there you go.
The hobgoblin ability is not that (obviously), though it can replicate (b), and do other things besides.
Does the ability work if the allies don't attack? What if there were 4 goblins hidden in bushes next to the party and 2 Hobgoblins at range with bows?
This, I feel, is an unfair situation for understanding the discussion -- the creatures here should not be set against a level 1 party: depending on the goblin CR (either 1/4 or 1/2), this is a CR2 or 3 encounter -- a difficult challenge for a party of level 2 or3 characters. It might be a fun situation to run, just not against level 1 characters -- absolutely the goblins should mop the floor with level 1 PCs.