“It’s something I really haven’t had for nine years consistently, is another big man down back, and the club has screamed out for it for a few years,” Jamison said.
Emphasis mine. I think Jamison is really enjoying not having to play on the gorillas that clearly out muscle him week in week out. He is able to be third man up a lot more and positions himself in places to block the run of other forwards. I don't think he forgot about Henderson or White, it's just that both of those players either play on the second or third string forwards, whereas Rowe can take the #1 forward if they don't have much run but a lot of muscle.
With forwards like Buddy, Tippett, Daniher and Carlisle et al. out there it's very important to have a c.198cm backman now - Rowe most certainly fits the bill for now and he also has controlled aggression and age on his side which allows him to psychologically impose himself on younger opponents.