Weirdly two other Japanese automakers, Mazda and Honda, said the same thing: that they had been testing improperly. Maybe this was brought up by some changes at the regulatory body?
Unlikely. Toyota's cheating came to light last year and Japan started investigating early this year. Once the others saw Toyota was under the microscope and they were probably next, they got their stories together and waited on Toyota to take the PR hit and got their admissions slipped in as an afterthought relieving them of later solo PR failings and potential investigations.
“Testing improperly”, well that’s one way to frame it.