TD:
I've already pointed out that 5:10 and 21:24 are two different lexical contexts and by my own reasoning
You're free to believe whatever you like. But your claim is not supported by the source material. Burton considers both examples to employ the exact same grammatical structure rather than 'two different lexical contexts'. So, claim that Luke 21:24 refers to an existing condition if you like, but don't claim that Burton supports your view. In fact, the only difference between the future 'trampling' and the other future events indicated at Luke 21:24 is that the others refer to a specific future event whereas the trampling would continue.
If anything, I'm claiming that Jerusalem was already under the heel of Rome at the time the words were allegedly spoken
'Already under the heel' is your own commentary, and has no bearing on the intended meaning of the future 'trampling'. As such, the association of the then-present situation under Rome (i.e. your own idiomatic description of the earlier situation under Rome as 'under the heel') with a future 'trampling' is an equivocation fallacy.