Shops that have expensive machines that cut 3 angles at once can really sink the valves and put big recesses that are not good.
Whether you own a $300,000 Newen valve machine or an old orbital Black and Decker seat grinder you still have to know what you are doing. Is the person doing the work qualified? Few shops today are when it comes to working on Hemi type heads.
Mark, sinking the seat to get that top 3rd angle was the practice with many shops using seat grinding equipment long before the form tool machine (Serdi and others) or computer computer controlled single point machine (Newan) even had been thought of. I have shops ruin heads using Neway cutters. It isn't about the equipment being used but the qualifications of the person doing the job. Remember that Michaelangelo did his best work in stone using a hammer, chisel and file. Burt Munroe did all of his work in a "rose shed" with fewer tools than most of you have in your workshop.
With the fuel available today it is important to toughen your engine against detonation. This starts by using wide valve seats. Those narrow seats are great for performance engines using race fuel, but on the street an engine with narrow seats will eventually suffer from detonation or pre-ignition. Often sooner than later.
Pocketing valve seats on a Triumph typically starts with the removal and replacement of the valve guides. Because of the structure of the head casting surrounding the valve guide is minimal at best, and does not support the guide equally around its circumference, when pounded in the head often goes in at an angle. If you don't want pocketed valve seats insist that the guides be drawn into the head with a proper tool. Also insist that the old guides be machined out of the head to insure oil wont be leaking down the grooves left as you bang the guide out of the head.