Is it correct to say that a researcher who is EU national and has worked for 10 or 15 years in a non-Associated Third Country is eligible for a European PF?

The duration of the time spent in the TC can indeed be deducted from the applicant’s research experience. The conditions are described in a footnote on page 8 of the GfA “Researchers reintegrating to Europe from a non-associated TC must be based in the TC at the call deadline or have directly moved to Europe (i.e. any EU MS or Horizon Europe AC) within the 12-month period immediately prior to the call deadline.” See also the MSCA Work programme 2021-2022, page 88.