The Allies limited the flanking options available (for both sides) by way of minefields looping and adjoining back to the northern escarpment (where ritchie surveyed +reserves held)...and of course strengthened by the defensive strongholds like Bir Hakeim. There was a gap left between the minefield and escarpment to create a gate for allied forces to use where the need arised in the open southern flank area (and beyond to try get at the german flanks). This meant the Axis hooks (given they are the attacking force) had to be planned/commited and risked at very high stakes generally (than they otherwise would be)....and if they went too far around, they would basically crash against the well defended escarpment area (with fresh forces and artillery cover).
Basically the Axis attack needed mine clearing in the spearheads for the mid-length flanking operations (one of which Rommel was in personally) and if discovered too easily and/or stretched too far at the opportune time...they would get routed....so Rommel knew he couldn't go all out on this kind of tactic (probably having long ago read and understood how Lee's battles north of the mason dixon line turned out regarding over-flanking commitments in contrast to Jacksons more appropriate use further south on home turf)...but just enough where the risk/reward seemed promising to him.
There were enough gaps in the artillery cover for Rommel to succeed combined with lack of response from the Allied forces at the critical moments....I also feel Ritchie overcommited to the mobile formations in the desert in his own counter-flanking+ open defensive engagement attempts, when they may have been better used in the defensive perimeter (esp around the gate chokepoint area)...and with very low frequency + organised and well spearheaded counter attacks. But its all in 20/20 hindsight of course.
I was thinking about the generic reluctance to loop out into the desert; it might have been inappropriate in this case, and in fact, the minefields got Rommel into trouble, when he found himself unable to push back to his original positions to the west due to the minefield around the 150 Brigade box. But in general, even when not facing set-piece defences like Ritchie, they did not really take advantage of the space to the south.
You pointed out a contradiction in Ritchie's plans that made a difference: he should have depended on his 'boxes' more. If you recall, the original model did shelter cavalry inside the 'squares'.