Lots of crappy v-brakes through the years have had no bushings. The brake arm simply turned on the post.
But, the spirit of the original claim in this regard is sill correct. Used with an arm with its own bushing and the problem of the OP is greatly reduced so long as not too much material was removed by the blasting. And, I doubt it was.
Your powdercoater should be severely browbeaten, btw. I would ask for a partial refund.
jim
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Cross Check Nexus7, IRO Mark V, Trek 620 Nexus7, Karate Monkey half fat, IRO Model 19 fixed, Amp Research B3, Surly 1x1 half fat fixed, and more...
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SB forever