A great topic. Ledi Sayadaw is correct in this case, IMO. He states
As for the exact nature, i.e., the swiftness, of mental phenomena, the understanding of which is the domain of the wisdom of the All-knowing Buddha, one has to accept the authority of the scriptures. Any talk about contemplating the three characteristics of mental phenomena is mere humbug. It is never based on practice, but only on hearsay from the scriptures. If someone were to try it, it would be a far cry from insight
So we hear of people thinking that because they feel ’ bodily vibrations’ that this is experiencing the actual rise and fall of the the elements…
We know that rise and fall is only known after the first stage of vipassana , and even that stage must be like a flash when the mind -door shows itself clearly and nama is understood as differentfrom rupa… And so anatta.
For the present moment: during the development of satipatthana the processes that understand an element know the nimitta of the reality-. So the actual reality has just fallen away but we still consider it as present moment.