Madhab of the salaf and the 4 madahib (Maliki, Shafi'i, Hanbali, Hanafi)

Salamo3alaykom, I don't understand when scholars refer to something as "madhabu as-Salaf u Saalih". Aren't the Madahib 4 which are already known? I don't want to discredit the biggest scholars of this Ummah, but why don't they say "manhaj salafu saalih" instead of madhab salaf as saalih? I don't understand because the madahib came after the three early generations and therefore those 3 generations didn't follow a madhab (please correct me if I made a chronological mistake, I'm definitely not good at Islamic sciences unfortunately). Can someone clarify and especially not put this question on check as unclear? Jazakom Allah