Because universal design is meant to provide the lowest common denominator of accessibility, it is appropriate for wheelchair users, those with walkers, and those walking without mobility assistance. It even works for those requiring assistance from caregivers or family members to move about from place-to-place either getting into or out of the home or moving about within their living space because of their inability to ambulate on their own.
People with joint difficulties in their fingers or wrists, or with range of motion in larger joints such as elbows and shoulders, that might normally have issues opening drawers or doors because of the hardware used to operate them - or in using switches, controls, or water faucets - find that the low physical effort and the easier to use features afforded by universally designed products enable them to function more easily and safer in their homes.
When strangers, neighbors, invited visitors, or guests visit someone's home, they will find that they can approach the front door, enter, and move about freely once inside because visitability is a compatible universal design strategy that allows people with and without physical limitations to feel welcome in the home - they are included and made to feel comfortable.
For anyone living in a universal design home - or visiting there - whether they have a limited reach or range or motion or no particular limitations will find the home equally comfortable, accessible, and usable to them. That's the point. Universal design is inclusive and accommodates a full range of abilities.
The fact that universal design features are meant to provide the same amount of access, the same degree of comfort and convenience, and general safety for anyone in the home - whether they live there full-time or not - means that it shows no preference or deference to anyone's ability or limitation and truly allows equitable use.
Whether a new home is being built or an existing one is being modified and renovated, and regardless of whether someone has a limiting condition that affects the way they move about in their living space, using universal design features and strategies will allow the fullest and most complete use of those homes. They don't need to be modified at some later date to provide that ease of access and use - it will exist now.
To that point, there are similarities between universal and adaptable design (adjusting for someone's changing abilities over time) because they both allow for increased access, comfort, enjoyment, and safety within the home by anyone in it. The issue is one of timing.
Making universal design changes to allow increased use of the home by anyone in it even when no particular limitations or medical concerns are being experienced by anyone in the household (or regular visitors) will mean that future needs can be accommodated without additional actions at a later date. On the other hand, adaptable design is making such changes when they are required so that it really is timing that separates the two strategies rather than any particular design treatments. This speaks to the inclusiveness of universal design because it provides for future needs and inabilities now - even when they might not exist.