like an engine, wear and tear is common but the higher the mileage, the lower the expectations of it working at optimal levels.

a 100k engine will have to work harder and won't produce as much power as it did when it was 1k. the same applies to turbos.

 

Did he specify if the shaft play was in/out or side to side?

There needs to be some shaft play, its the space between the shaft and bearing for the oil to get in and do its thing.

Personaly I think 2mm is a bit much and it may need a rebuild in the near future but that could be argued in sure.

 

Like asked above, is your play axial (in/out) or lateral (side to side)? 2mm is too much play in either direction. There should be virtually no axial play and a only a small amount of lateral play.

Unless things really get worn, they should boost fine, but will let some oil around the compressor and/or turbine oil seals, making a smoke screen when you hit boost.