Further, the other detail differences would make Luke's version an extremely poor and inaccurate paraphrase of the Olivet Discourse, were it the same speech. I hold Scripture to a higher standard than that.
The widow's mite affair doesn't prove anything simply because it doesn't provide any time clues beyond appearing right before both Mark's Olivet Discourse and Luke's Temple Discourse.
Interestingly, for about three years, I held this view and couldn't find anyone else who expoused it. But a few weeks ago, Missler released a briefing pack agreeing with me. That doesn't make my view right, but it does mean that I'm not the only one who noticed these differences.
When it comes to differences in what appears to be the same event, I've always attempted explanation first from the "Various perspectives" viewpoint.
If I'm standing on the north corner and you are on the south corner, there is a car wreck, and we are asked to write an account of the wreck, then we are going to write about the same thing from our particular vantage points. Both can be entirely true AND have differences.
Luke says that in producing his gospel he meticulously gathered the accounts of those things that happened.
1 Inasmuch as many have undertaken to compile an account of the things accomplished R1 F1 among us, 2 just as they were handed down to us by those who from R2 the beginning were F2 eyewitnesses R3 and servants R4 F3 of the R5 word, F4 3 it seemed fitting for me as well, having R6 investigated F5 everything carefully from the beginning, to write it out for you in R7 consecutive order, most R8 excellent Theophilus; R9 4 so that you may know the exact truth about the things you have been taught. R10 F6
Both Matthew & Luke are faithfully reporting. IMO, It is better to see a single discourse, than to attempt to come up with 2 extremely similar episodes that are within hours of each other. I find that view to be overly frightened.
It is the UNTIDINESS of the gospels that verify the integrity of the reports.