Interesting point, but I think you have to back off the WTS a bit here simply because of Ezekiel 4:6 which notes the formula of "a day for a year."
"A day for a year"?
Now that reference alone inspires a double application. You know? How is a "day for a year" going to ever be applied? Problem is, once you apply "a day for a year" to one prophecy, then you have created the logical context for applying it to ALL the prophecies.
Now look how that is fundamentally confirmed. Let's say the "70 weeks". That is 490 days. Clearly this reference the coming of the messiah after 69 weeks. The messiah did not appear 483 days after Jerusalem began to be rebuilt. He appeared in 29 CE. Now is that relevant to the "day for a year"? What if 483 days is really 483 years? So we ask, as part of "proof in the pudding", whether or not the appearance of Christ in 29 CE in any way is connected to 483 years? Well, per the VAT4956 and the Bible, the 1st of Cyrus occurs in 455 BCE, which is when the Jews first began to rebuild in the Fall. That is, the VAT4956 confirms year 37 of Neb2 to fall originally in 511 BCE. The SK400 confirms year 7 to fall in 541 BCE, the same dating! That means 455 BCE was the original 1st year of Cyrus. That is when the "70 weeks" begin. If so, then the messiah should have appeared 483 days later, which he did not. But if we apply "a day for a year" formula, did Jesus appear 483 years after 455 BCE? That is, in 29 CE? Answer. YES!
So if the "70 weeks" prophecy clearly was meant to be fulfilled in connection with "a day for a year", then, of course, there is going to be an obvious academic rush to apply "a day for a year" to all the other chronology prophecies in Daniel. That means the "7 times" prophecy which converts "7 times" to 2520 years.
So even if we see this fulfillment somehow not being fulfilled, you can't blame anyone for making the application because it is not an inappropriate application outside what the Bible itself requires, which is a fulfillment of "a day for a year."
So in all honesty and to be fair, you can't really in this case blame the WTS for converting days to years if it's right there in the Bible.
So, in other words, we should ask: Did the WTS on their own decide to convert a day for a year? OR Did they get this idea from the scriptures themselves?
So you see? In this case, they sort of had no choice? Right? "A day for a year" has to be explored. But when you do, it turns out to be accurate.
Same with the "7 times". Unfortunately, the WTS was deceived by the revisionism of the Persian Period and ended up with a distorted date for the fall of Jerusalem in 607 BCE so they think Christ returned invisibly in 1914. The correct date is 529 BCE, which means Christ was to return in 1992, which he did! He actually did! I'm a personal witness to the return in that date! That is only possible when you apply "a day for a year" formula.
So really, folks, in all honesty, there's no choice. Ignoring "a day for a year" thus is rather dishonest or naieve. You can't blame the WTS for applying "a day for a year" when it is in the Bible. Sorry. But more importantly, the "proof is in the pudding." The fulfillments do convert a day for a year in all these prophecies!
1. The 70 weeks shows Christ appears 483 years after 455 BCE, the 1st of Cyrus. Fulfilled.
2. The "1335 days" prophecy shows Christ appearing 45 years after the final return in 1947, in 1992.
3. The "7 times" prophecy, 2520 years after the fall of Jerusalem which JWs incorrectly date to 607 BCE dates his return in 1914, but the correct date of 529 BCE dats his return in 1992, just as #2 above.
All these apply the "day for a year" formula and it works! So a double fulfillment and converting "a day for a year" is very much fundamental in scripture and correct.
So GET PAST IT, folks. There is a double fulfillment here, unless you're blind, which I suppose, I'm finding, is often the case. But it is voluntary blindness: see no evil, hear no evil, speak no evil, right?