In retrospect, the reason the valve wiki says to wait "a frame" is probably directed at mappers firing inputs via entities... who knows what order those actually get fired in when you have a list of different inputs that happen on the same trigger.
In sourcepawn... you can actually control that. ;p
I still have no idea what the difference between SetParentAttachment and MaintainOffset is. I tried both and they seemed to work identically, both teleporting the entity to the attachment point. I have no idea what "offset" they're talking about. How far the position of the child is offset from the parent? Doesn't seem like it, since it just teleports to the attachment point anyway...???