I would assume that the author meant to mean "growth in the supply of bitcoin." Which seems like a reasonable error to make, because printing money typically has an inflationary effect, even if it isn't technically synonymous with inflation.

Maybe dilution is a better term? If all other factors could be held equal, then the real value of the ~6BTC reward for mining a block would, in effect, come from a tiny reduction in the real value of everyone else's BTC assets that would result from the supply of BTC having increased.

It creates an interesting situation. Right now, the cost of actually operating the BTC network is largely supported by every single person who owns BTC, proportionally to how much BTC they actually have. As the mining reward continues to taper off, that is going to shift toward the cost primarily being covered by transaction processing fees. That will change something fundamental about the economics of Bitcoin, although I'm not sure exactly how.