There are several names that apply to aging in place design. Universal design is an overarching concept that encompasses aging in place specific design as well as making the living space suitable for others as well. Visitable design is a similar concept that addresses accessibility and mobility more than specific features in the home. Adaptable design is the moving target that makes changes to someone's home to adjust to the ever-changing needs as they become evident and need to be addressed. Accommodating them prior to their actual identification is a universal design process because the end result of a universal design project and an adaptable one are nearly always the same in look, feel, and purpose. Only the timing and intent (reason for doing it - now or as it is needed) differs in the two designs.
Home modification treatments that some people may term adaptable because they relate to a change in a person's abilities over time - and could seem so at first glance - actually fall into the realm of preemptive design (my term). Installing wooden wall blocking just in case grab bars, fold-down shower seats, or railings in the hallways or other living areas may be desired at some future date is clearly preemptive. There is nothing in this type of approach that is appealing to someone's needs now - rather how those needs might change in the future. They might never change to the point where the preemptive design would be needed. This is not adaptive as nothing has been done to change or modify the space to help someone who needs it now.
Similarly, putting in chases to carry electrical or plumbing lines at some future time when it is deemed necessary to have them, or roughing in plumbing or drain lines so that additional plumbing fixtures can be installed in more convenient areas later is good planning, but this has nothing to do with adapting the space to appeal to someone's changing needs.
The key with adaptive or adaptable design is that it must be something that is done now that wasn't necessary in the past in order to make the life of someone in the home more enjoyable or functional. Enlarging doorways, removing carpeting in favor of a hard surface flooring, lowering or adding lighting to illuminate certain spaces, removing cabinet doors or otherwise adapting them (retractable, for instance, or removing the sink base altogether), changing the way faucets are accessed and operated, changing out appliances with ones that can be operated from a seated or low-vision ability, and other such changes are examples of adaptive design because they change the home from way it has been to the way it needs to be.
The easiest way to look at the design changes that might be contemplated as they relate to aging in place issues and appealing to specific requirements of the individuals in the living space is that anything done to improve a current (operative word) situation is considered as adaptable (changing or adapting from something not working so well to something that can work better), and anything done to impact or affect the future (operative word) needs or condition is termed preemptive - just in case or getting ready.
Both types of design have merit, but we need to call them by the right name according to their intent and the time frame they are serving.