I would think it is AP count. (not 100% sure)
With AVC, if you trying do control part (re-mark, drop,etc) I think that would be more resource intensive & leading to WLC crashes/meltdown in large environment. Below bug may be one of reference that got many cases attached in 7.6/8.0 versions
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuq97965/
As long as you use it to get visibility (simple netflow export), I do not see a major issue of enabling that feature.
HTH
Rasika
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