Exchanges can certainly fractionally reserve but that doesn't mean there's more bitcoin. There's simply more IOUs. But dont get it twisted, an IOU is not the same as the real thing.
An interesting thing to note... Bitcoin sorta does technically have inflation before it reaches hard cap. The difference is its a programmed and scheduled inflation rate. As coins are mined and released into the wild, technically that's inflation. But the difference here is that everyone is on a level playing field and everyone knows the score. Full transparency and no one can unilaterally decide to adjust the inflation rate.