Elazar Yechiel Bernstein asked:
Surely Rav Hamnunah knew dikduk so why did he make any different of a drasha than Rav Nachman in umetzach isha zonah hayah lach?
The Kollel replies:
He explained the verse as saying that the Metzach which is fit for an Ishah Zonah, he had (that is why it is appropriate to be in the past tense, even though he had not yet sinned with a Zonah).