As an engineer that's been tasked to interview in this style, I have to say that it's possible to do with a few candidates without too much interruption to my r

As an engineer that's been tasked to interview in this style, I have to say that it's possible to do with a few candidates without too much interruption to my regular duties, and it's actually my favorite method of interviewing. Having an inbound candidate build some simplified version of the thing we're making is extremely helpful and doesn't cost too much. You can easily define the simplified work sample project once and reuse it many times without spending too much time on it. The parent's criticisms are valid because there almost certainly won't be some work sample that fit all of the criteria mentioned and is actually a part of the product. But a work sample of a simplified version of the product they'll be working on is absolutely easy to do and insightful for both you and the candidate. Maybe they just really don't like the kind of thing you're working on. Well, this gives them a chance to dip their toe in the pool.