How would you handle whining ~17 months?

My 17 month old tends to have situations where he will mostly whine instead of cry. When it happens I try to listen to what he’s trying to tell me, figure out why he is whining and encourage using words instead. If he’s whining but doesn’t want anything specific I try to offer kind words / comfort. Basically I always try to respond and find a solution.

My MIL who watched toddler for the weekend while we were away told me that every time he whined she would whine back at him jokingly to get him to stop. I know from my husband she started grounding her kids for whining at a young age and often explains how she “hates whiners.”I don’t think I’m comfortable with this and it didn’t occur to me that whining is something I should be actively trying to “stop” him from doing.

I guess I am asking, how do you approach whining at this age? What is the age appropriate response and should it be stopped?