We have no knowledge that vac ever used string detection. If they would, it would hit more ppl than just poly hacks.
I suggest you to read this : https://www.mpgh.net/forum/showthread.php?t=1083252
Explains quite well on how to trick VAC (well you must think a bit on your own).
If you want to make a pattern scanner to find a certain address in memory you will mostly use wildcards ('?').
In poly hacks we are using junk codes, mostly just the [add junk/] macro that will add 5 random variables.
So what will vac do? Easy, they will wildcard the places where the junkcodes are added ('? ? ? ? ?') and generate a signature.
But yes i dont understand. We have 100% proof that VAC uses signature based detection, just because someone think they used string detection doesnt mean vac did.
Atleast this is what i think. Even if they used string detection, we can easily change the strings.