The holes in new bushes are under size by design, (they don't compress as they are inserted),
Jim,
I'm happy to defer to the pros. The explanation I was given originally ( and admittedly this was in respect of a very venerable MG) was that because the bush- for that car at least- was essentially phosfor- bronze with a white metal facing then because it was interference fit, there necessarily had to be a degree of compression of the inner diameter and, of course, had to be reemed
Typical amateur, me- knows just enough to be dangerous!

regards,
G