Tom is very thorough about his work, keep in mind that shops may send cylinder heads out to have the valve work performed.
When I send a cylinder head to a machine shop I request that they "do not bead blast" the head, it is sand/glass and I do not want it to become a potential problem. This goes double for the later model cylinder heads confirgured with multiple camshafts, bores for the followers, and small passages for delivering lubricant.
The abrasive material used for bead blasting does not comfort me when it is used on cylinder heads!
Procedures vary form shop to shop so I encourage you to ask a shop how they address cylinder head work. If they send the work out than it is in your best interest to request "No bead blasting" on your cylinder head.