But "officially" has the FCC ever put the top hat clarification in writing and published their interpretation?
Short answer: no.
...which should not be taken to mean "anything goes," obviously. Nor does it necessarily follow that we would WANT them to clarify it in nitpicking detail, either. The Canadian RSS-210 rules do that in a few cases, and the results are not pretty. Much better, IMO, to make reasonable assumptions in our individual cases and be prepared to explain why we believe our own installation complies with the literal plain-text wording of the rules.
Longer answer: no, not exactly, but we have been given some small instances of guidance; not all of which has been widely accepted.
Some of those "Philly lawyers" of whom you speak like to argue "original intent" of the rules as being garage door openers, and insist that only a single run of wire was ever intended. Well, that's not what the rules SAY, and the FCC has made it abundantly clear (for example, in the 2005 R&O on the earlier proposed amateur LF allocation) that Part 15 exists to facilitate communication and experimentation on a non-interference basis, not to stifle it. So, no, we're not really bad boys getting our thrills from living on the edge of the law here. But that still doesn't clarify 15.217(b) when something other than a simple length of wire or a small-diameter pole is involved.
One of the more popular "translations" of this particular rule, as you may remember, was known as the Ken Cornell interpretation. Ken felt that any antenna which you could fit into a cylinder 50 feet tall and 50 feet diameter ought to be compliant. Personally, I think such could reasonably be argued, given the inherent inefficiencies at 1750 meters in the best of cases, and it certainly would have eliminated any ambiguity over what counted and what didn't. But we know for a fact that the FCC DOES NOT AGREE with that interpretation. In the big Part 15 rewrite of the late 80S/early 90s, LWCA filed comments through the umbrella club organization, ANARC, in support of the Cornell interpretation, and the Commission specifically and very pointedly denied that request. Case closed, for all practical purposes.
At the opposite extreme are a couple of interpretations that were allegedly given to some hams in person by FCC inspectors over the years, to the effect that every single piece of wire in an antenna top hat counts toward "total length." (Now, the rules don't SAY THAT, either, but if an inspector tells you to shut down for any reason, the only thing to do is comply and then hope for someone in DC to give you a reasonable hearing.) Similar answers were given to experimenters in a mediumwave group about a decade ago when they emailed Commission staff (alas, you'll have to trust my memory for that, because all my correspondence and list archives from before the Big Crash of '016 are gone off to the cyber afterlife now); but since the answer also impacted LF loop antennas under Part 15, there were some who simply chose not to believe any of it, so even if I still had that correspondence it might not be too helpful.
Of the more reasonable traditional interpretations, one holds that if individual conductors in a top hat are bonded together into what is effectively a single conductor, they amount to one structure whose radius should be added to the vertical run for determining total length. (Individual wires, such as the top of a T or L, probably must be counted individually.)
Now, there IS one more or less formal bit of guidance from the FCC on antennas that do not consist of a simple run of wire, but are made from large diameter pipes, metal plates, or similar large, non-traditional conductors. It could probably be applied quite reasonably to top loading. Problem is, that document was also among those lost in the Big Crash, so I hope someone else remembers it and can come up with it, because it may help with this question. The essence of it, though, was that "length" in such a case meant the longest diagonal measurement of the surface or structure.
Again, I hope someone will be able to find that example. Bottom line otherwise: you're on your own, but if you can at least tell a reasonable story of why you believe the antenna fits within the plain-language reading of the rules (ie, not a big stretch of logic nor too nitpickey) you're more likely to survive any however-unlikely FCC inspection with your dignity and household finances intact.