I have seen cases where the timing gear starts digging into the cam retaining plate, and in a case like that the thrust bearing would probably be a good idea. Usually that's not an issue, though. I've used those thrust bearings myself with no problems, but if something bad were to happen and the bearing is damaged all those hardened steel shards will go into the engine, potentially causing a ton of damage. Those needle bearings are small enough to sneak through the oil pump screen, jam the pump, break the cam gear and/or the distributor gear, etc.
Unless you are building a really high HP engine, I don't think the thrust bearing setup is worth it
