That's something I really don't like, is...there can be engineering reasons for those lockout nubbins to be there. My Craftsman V20 chargers have two lights on them, one labelled "V20" and another labeled "V12". Which suggests there were plans to make 12 volt batteries in this form factor, I guess for a "Flex Volt But Worse" idea that never emerged. Some tools might be 20V only or 12V only and you would NEED to prevent them from interchanging or else you'll let out the magic smoke. Or in the case where the pinouts are different for some reason.

And sometimes the marketing department put them there so that most of the population will think they need to buy more batteries when there's no technical reason for them to do that. Which is why I have a bit of a problem in general with one company selling interchangeable products under multiple different brands. But that's a whole other bag of cats.

I also haven't really got a lot of hands on time with DeWalt's 20 Volt tools or batteries, I do know that some of the Brushless Craftsman tools bear strong family resemblance to DeWalt's line, so I imagine the same engineering firm is designing tools for both.