The concept of infinity can be quite challenging to comprehend, and it often leads to paradoxes and counterintuitive ideas. Regarding your question, it's important to note that infinity does not imply that every possibility or variation must occur. Infinity simply means that there is no upper bound or limit to a certain quantity or extent.
In an infinite universe, it is still possible for certain variations to exist, such as an infinite quantity of an item with volume. However, the existence of infinite variations does not necessarily mean that all possibilities must be realized. It's entirely possible that some variations or configurations may never occur, even in an infinite universe.
To illustrate this, consider the set of all even numbers. This set is infinite, as there is no largest even number. However, within this infinite set, there are no odd numbers. Just because the set is infinite doesn't mean that it contains all possible numbers.
Similarly, even if the universe were infinite, it doesn't necessarily mean that every conceivable variation or configuration must exist within it. The infinite nature of the universe simply implies that there is no limit to its spatial extent or the potential for variation, but specific arrangements or configurations may or may not occur.
Therefore, the fact that there might not be an infinite quantity of an item with volume in our observable universe does not prove or disprove the infinitude of the entire universe. Our current understanding of the universe's size and structure is still a subject of ongoing scientific investigation and exploration.