but we do have a "lock-date" on our loan input sheet. If, for any reason, the rate changes during the process, the date is updated
If the rate can change during the process then you don't have a locked rate and I would argue you final rate was set the date of closing.
just don't know how we can wait until the closing date to compare the APR to the APOR.
As David stated, unfortunately TIL requires this. As an example when you complete your ETIL and the APR is 6.149 and the APOR is 5.000, you're under the 1.5 for first liens loans. On the day of closing lets say your odd days interest are longer or you have some other PPFC charge that is just a bit higher than you estimated and it brings the closing APR to 6.151. You're not out of tolerance so you don't have to redisclose for MDIA purpose but your APR is now over the 1.5 threshold therefore making it a HPML.
IMO if you are not willing to use lock agreements then you have to accept the fact your rate is not set for the last time until you close the loan because the rate has the potential to change until that date and just because it didn't does not mean the rate was set for the final time 15 days ago because you checked the rate as the date of closing and it was the same therefore the rate was left as is or IOWs it was set for the final time.