Hello.

I tried to select Flat End Tapered mill for the countersinking operation and get the warning message.

After that I tried to select some other milling tools and always get the same message. It seems SOLIDWORKS CAM has check of the tool type for different operations.
I think it is not good idea to use this check, because very many different milling tools have ability to work as drill or as reamer.
I think, it would be more correct to remove this check from such Hole Machining Operations:
1) Center Drill;
2) Drill;
3) Countersink;
4) Bore;
5) Ream.
Such check is good for Tap operation.
As a workaround, I created the countersink tool with same geometry, but after post-processing there is unnecessary tool change in program.