possessives - Why is "several two hours' meetings" wrong?

Why is "several two hours' meetings" wrong? Any insight will be greatly appreciated.
It is from an ECPE practice exam grammar section question.

The boss won't be able to see you today as he has got several______meetings.

a) two hours

b) two-hour
c) two hours'
d) two hour's

Answer

We’ll get the simpler cases out of the way first: two hours meetings and two hour’s meetings are both wrong. The first combines has two nouns in a row (hours and meetings) without any kind of word to relate them. Some nouns can be used be used as an adjective, but hours isn’t one of them (hour could be, as we’ll get to, but not hours). And two hour’s meetings is wrong because if there are two of them, then the hours are plural, and the plural possessive is hours’, not hour’s.

The hyphenated term two-hour combines the two words into a single adjective: whatever noun two-hour modifies, we know that noun had a duration of two hours. So grammatically, this is valid. Furthermore, this is the correct answer to the question simply because this is how English speakers would say it.

It is fairly common to put a hyphen between two adjectives to indicate that the first adjective is modifying the second, rather than both of them separately modifying the noun. Contrast with two hour meetings which would imply two meetings, each an hour long, rather than a single meeting that was two hours long. (Though, to my ear, hour meeting sounds strange and I would very likely expand it to two hour-long meetings—but I would not say two-hour-long meetings. I am not personally sure why that is. The difference may very well to disambiguate between the two possibilities. Also note that the preceding several rules out two hour-long meetings—either there are several or there are exactly two; using both adjectives is confusing and wrong.)

Now then, on to your actual question.

The phrase two hours’ meetings is grammatical, and could be used. You hear things like in two hours’ time occasionally, meaning “two hours from now”—but it sounds somewhat archaic, makes me think of a Victorian-era British gentleman. English speakers will understand two hours’ time. But I cannot think of any other noun that hours’ could be applied to—really, what does an hour possess other than time? I guess you could use two hours’ minutes to mean 120 minutes or two hours’ seconds to mean 7200 seconds, but I have never heard that usage and would be confused by it, probably requiring confirmation or clarification. But two hours’ meetings? A meeting is not something a pair of hours could possess. That makes the possessive here nonsensical. Which doesn’t always stop English, of course, but in this case it does. Ultimately, as with everyone else, two hours’ meetings is wrong simply because English speakers do not say that.