From the rear or sides, many of these units would be exceptionally weak. If nothing else they would rapidly lose the "clash of shields" and get compressed into a dense tangled mass. Instead, the hops spread out into a wide circle. This is unrealistic, since they should get pushed back by the massed organized ranks attacking them. I think MTW did a much better job reflecting flanking effects. Rear attack on a spear column leaves them completely vulnerable. The rearmost rank will have to confront this virtually alone, and without support.

There was a reason that the phalanx fell out of favour: mobility, they were hard to maneouver meaning that they had trouble pressing home an attack without serious risk of being attacked at the rear or sides. Also, in reality units being attacked from the flank, can only put up a modest defense. There simply won't be many men to confront the threat and the men at the corner are being shoved and stabbed at from two or three directions at once.

The morale effect would be devastating. Pinned at the front, unable to put up a good fight against the side or rear. The tendency would be to fall back from the multiple threats to live a few more minutes (into an even tighter mass.) Didn't Hannibal crush the Roman legions in similar fashion at Cannae? (Not spear units per se, but the effect of flanking on morale to even disciplined troops was clearly demonstrated--and pure spear units would be in even worse shape.) Hannibal was out numbered 2 to 1 and faced disciplined men of high morale. I'm sorry, but MTW got this effect right.