They have of course other methods - did u have all accs full separate - every acc has own paypal , u do not trade between etc? So unlucku, sorry for your lose. Since december 18, cumulative 15+12 toons (2 dudes) without scratch.
VMWare + full separate just lowering odds, nothing more. One multiple hashid is just praobly autoflag by default (no virtualisation)
Despite VMWare i have full separation all accs (gold for items traded via aouction house), separate paypalsand every 2-3 toon got different ip.
Lowering odds, never can be sure. Still 1.1 year without 1 ban.
Need to add that I use some old version od DBBeta and old trnity- hasnt upgraded it for like 3-4 months (just adjusted item rules)