In the past I have never ever received a hotel booking by KLM when I got stuck at Schiphol airport, even being Platinum. Always had to book one myself and claim the bill to KLM. Always got reimbursed though.
But this very rude attitude (in combination with April changes of course) made me change from Skyteam to Star Alliance. Now flying Swiss and Lufthansa, got stuck plenty of times in FRA and ZRH, got hotel night without asking.
For this week's disruptions, following is clear:
KLM has the obligation to reimburse the ticket price or rebook you on the earliest available alternative flight, no matter in which booking class you are booked (same cabin class though).
Only in case you want to rebook your (unflexible) ticket to a later date, which KLM is not obliged to do, they can apply whatever rule they want, such as rebooking in the same booking class.