As much as we want to embrace a particular design or idea that is marketed as or touted as a universal design product or solution, we can't just rely on the labels or descriptions that someone wants to attach to it without verifying it bu what we know to be true. If someone mistakenly believes that something fits the category, based on their own interpretation or from what they have read or been told, and we can't agree with their premise, then the label doesn't hold.
Universal design is pretty simple. There are seven basic principles that North Carolina State University crafted in 1997. They have not changed in the ensuing 20 years. There is some overlap among the seven criteria, but it is fairly easy to compare a product, solution, or application to find out whether it meets any of all of the established criteria. Just wanting it to align with some or all of the principles with no visible evidence that it does is not good enough for us. Here, desire is outweighed and overruled by function.
Some designs that people want to use have specialized functions that apply to a particular need that someone has - be it mobility, sensory, or cognitive. Because it is meant to serve a certain aspect of the population and not the general public, it cannot be regarded as universal design - no matter how much someone wants to persist or claim that it does. There is absolutely nothing wrong with having aging-in-place solutions that appeal to someone's specific needs, but these won't fall into the category of universal design unless they have much broader appeal also.
Since universal design is a very inclusive type of design, it is no respecter of ages, physical size, capacity to understand how something works, or physical ability to operate something. That's why a couple of the principles of it are perceptible information and low physical effort.
If a first grader can use something well - say a digital thermostat (although they don't need to know what the actual numbers that they read mean in terms of relative comfort) or a rocker light switch - and a grandparent (someone even into their 90s) can do the same - whether they are using mobility assistance or not and regardless of the the strength of their vision or any joint difficulties they may possess - that item is a universal design feature. If only one of them, or neither of them, can use it as it was intended, then it is not universal.
If something seems like it would be a good design to create or install it in a certain manner, ask how the first grader and the grandparent would relate to it as well as others who might have various limitations. That should be enough to decide if something generally can be used by people in general or if it is more limited to just certain persons. Universal design means just that - essentially being for everyone.