May I suggest that the name 'Perez' here has/had more to do with people of Sephardic Jewish background in Europe.
Since Spain ousted them in 1492, people settled elsewhere and the surname lived on.
See e.g.
https://de.wikipedia.org/wiki/Jizchok_Leib_Perez or
https://www.jewishgen.org/infofiles/breslaumarrgs.html (search for Perez).
Moreover, Spanish sounding surnames have survived outside Spain due to its dominion of parts of Europe in past centuries.
Not related to 'our' Horst Perez, but in 1954 a man with the same name was convicted of practicing medicine without proper credentials. He was born in Konitz, West Prussia in 1920 (now Chojnice, Poland). Surname therefore not altogether unlikely in those regions.
Regards, Leendert