There is a real thing that can lead to lower diversity. It goes something like this: people who took CS at a university, and who did unpaid (eg open source) work while doing so, make great developers. Yay! Let's make sure everyone we interview did that.
Sometimes these companies come to realize that there are great developers who didn't take CS at university, and also great developers who did, but had a job while they did so (or small children) and therefore no time for open source. They rethink their interview process, which is excluding these people for no good reason. They decide to stop asking everyone to reverse a string in place in C or how to get the people across the bridge with the flashlights or why manhole covers are round, because they have come to realize that while some great developers get these right, not all do, and asking them is reducing the pool of developers they can hire from.
Changing the questions you ask everyone so that they actually test for what you need is a great idea. Asking "easy" questions of the "under-represented" group suggests such people aren't as good but will be hired anyway. This is so awful for everyone. Don't do it.
If you have reason to believe that women, nonstraight people, noncis people, those with physical disabilities etc bring a little something extra to your workplace, so that you would hire them even if they were technically less excellent (setting aside the issue of whether or not your current interview process measures technical excellence with any accuracy) then the right thing to do is articulate what that something extra is (empathy, multitasking, resilience and personal strength, intuition, whatever) and ask everyone questions designed to reveal that, and take the answers into account in your deciding. You may find that your totally-doesn't-appear-diverse on the resume and by physical appearance candidate was raised by two mums or has a brother in a wheelchair or grew up very poor or is an immigrant or in some other way is in this pool of different-strengthed people (or just plain is empathetic, strong, multitasking and intuitive despite a background that wouldn't imply it) and be able to point out that even though this candidate doesn't tick bureaucratic "we have black/gay/female people here" boxes, this candidate brings those strengths. And of course, if your presumption about what diverse people will bring you is true, all kinds of "diverse" candidates will do great on this section of the interview, telling you stories of leadership, perseverance, emotional heroism or whatever, and you will have a powerful and strong real reason to hire this person beyond the box-ticking.