As you were/are not qualified to fly an N-Reg aircraft then none of your flying could be as PIC, and all of your flying has to have been logged as PUT.
As this was not with an EASA Instructor they are not entitled to sign you off for your Tailwheel Differences Training - so you are still not entitled to fly a Tailwheel aircraft; and none of the flying can count as the 1 hour Dual required for SEP Revalidation by Experience - as this also has to be done with an EASA Instructor.
@LA: The first part I easily get, but struggle with the second. Do you have a reference stating that only an EASA instructor can sign off the logbook for difference training?
The only thing I find is, endorsements are signed off in the relevant logbook by "an instructor", no more details. I would understand the need for a "honorable and certificated and dependent EASA instructor" for putting a sign off in an EASA Part.FCL license, as I guess a FAA instructor would not be allowed to sign the holy EASA papers, but so far endorsements are logbook only. I also did not find a requirement the instructor has to be FI/CFI/FE or whatsoever, but only "suitable". Which brings me to the question where the hack did they define what an "instructor" shall mean? Sorry, if I am too dumb to find it myself.