Yeah, they quite often oversell on AMS-EDI and vv. I had a 100% operational upgrade success rate on EDI-AMS in 2005 when the KLMuk one-class product was first replaced by the two-class. I regarded it as payback for all the years spent paying full price for an all-Y cabin
As for operational upgrades on long-haul out of AMS, consider yourself very lucky to have got even one in your lifetime of dealing with KL gate agents. Ask on the KLM forum and you'll find plenty of folks who still have a 0% rate after more than a decade as a top tier. The whole process is much less transparent, more random and more badly-managed than it is in the US.