I quote ISO/WD 8601-2:
Representation of a decade must be exactly three digits, leading zeros, if any, must be included. Thus the time interval 200 through 209 is represented as ‘020’ and NOT ‘20’; the latter would represent the time interval 2000 through 2099.
Here you can clearly see that the ISO definition of a decade is in keeping with the common understanding, not whatever oddball misunderstanding you've chosen to promulgate.