Maybe I misunderstood what I read or it was wrong but this is what I've been doing for probably close to 10 years without any issues.
Have I just been lucky?
Possibly.........I know folks who should but have never paid estimated taxes and have never gotten a penalty and therefore see no reason to change. Perhaps it is IRS priority.......the penalties are relatively small and may not be worth their time and effort.
However if you study F2210, you will see that IRS assumes income is received evenly during the yr and expects payments accordingly. It is ok to pay early so the payments are front-loaded during the yr. However if you only pay 1 estimated tax payment in Q4, that is an easy sign that there might be late payments in the earlier quarters. If you can prove that the payments matched the income timing wise you are ok but it is a bit of work to do that.