He is referring to a fluted bolt...many makers do them and many will flute your bolt if you want it done.
Ah, gotcha. So, fluting will not weaken the bolt? I assume it is only deep enough to be decorative. How much weight could really be removed?
On a SA Rem 700 bolt the more aggressive fluting ("Ti style") shaves about 0.7 oz. On an LA about 1. Remington 700 Ti bolts came that way from the factory as do many custom actions. Less aggressive fluting saves less weight, though I don't have actual figures because I don't have any bolts so fluted.
It supposedly aids bolt cycling but I have never had an unfluted bolt lock up due to debris. And I've had stuff get into my bolt channel a few time. Have also heard that it helps to distribute lubrication, but I don't lube bolt bodies either.
Many smiths will flute a bolt. Heres a pic of a Karl Kampfeld fluted (and webbed) bolt on a 7: