i think what hes trying to get at is the wastegate does control boost, but if the wastegate is positioned poorly on the manifold, ie not letting all exhaust pressure hit the valve, you would get a boost spike, because your not building the 1bar pressure you would normally be building but the exhaust is actually getting past the gate since its not positioned properly. wastegate placement has alot to do with how much boost you run, and if your going to get boost spikes/creep. The wastegate choice is determined on the turbo and boost level you are running, for instance my friend turboed a b18c5 with a gt3076r bb garret turbo, and he was running 10psi on a 38mm wastegate, but because of the lower pressure and fast spool with the ramhorn he would boost creep to 12-13psi instead of the 10 the wastegate was set for. so he went with a tial 44mm wastegate and it controlled the boost much better because of the lower pressure. so it does matter what size wastegate,turbo you run and also the wastegate placement, poor placement= boost creep or a spike. also i get what hes trying to say about how 4clys running 35+ psi hardly need wastgates, some cars with bigger turbos that are more efficient than what the motor car produce have trouble running over a certain boost level. Example, i remember jeff frank had his blue turbo eg hatch with a dohc zc with a big t4 on it, with the wastegate on there it wouldn't hit over 18sih psi, and when he took it off completely it would still only hit 22-25psi i belive... because the motor had trouble spinning the turbine up in its efficiency range.
saying the wastegate placement and sizing the turbo up to the wastegate and pressure you want to run is like saying 2" exhaust will spool your holset faster than 3" would
plus if you have ever ran a log manifold with the wastegate running off the #4 runner only you would know about having boost control problems, my dsm had major problems controlling boost with the cast manifold and shitty wastegate placement on high boost, i made a tubular manifold with the wastgate coming off the collector and has no problems running 32psi