For those who don't get how the 80% rule favours the home team ...
The slots are normally for whatever usage an airline desires. A few may be tied to specific destinations but most are by carrier. So the home user (KLM here, BA at Heathrow, etc) can flex things within the slot season, often by just a few minutes, so they quite readily do conform overall to the requirement. They may not be able to get extra flights but they don't run the risk of the use-it-or-lose-it-rule.
Visiting carriers, especially low frequency intercontinental ones, do not have this capability, and all-cargo carriers whose business flexes with customer demand even more so. Because much freight is nowadays belly cargo rather than in freighters, apart from the worldwide small package specialists, all the mainstream freight facilities are at the main airport, for interlining, agency offices, 24 hour service, etc, so going off to an obscure alternative is impractical. But it even applies to low frequency passenger flights.
For carriers from countries without slot restrictions (which, worldwide, is most of them), it is thus particularly unreasonable that while the likes of KLM or BA can readily operate back to their territory without restriction, the restriction is very much seen as a one way street. Open Skies, but the authorities have found another way round it.