Not just around M113s, standard setup for all armour.
Yes, those are M109s with ACAV turrets.
The fencing would get in the way on the move, get in the way during dismount and catch in the brush,
and the mud etc. Screens of fence mesh were tried on the Sheridan, but were soon ripped off in the
jungle.
The slat and bar armour worked on the monitors and the riverboats, but I doubt it would have worked
ashore for the same reasons mesh didn't.
BTW the Oz Centurions had their trackguards cut back front and rear and the stowage bins reinforced,
the former to reduce mud clogging and the latter to keep them form being ripped off in the bush.
Truthfully, I doubt if many of the current 'desert warfare' biased systems with their festoons of slats would
do that well if suddenly dropped into a wet, densely forested tropical environment.