No, that's kinda my point, there's no reason for me to pronounce it /sɑm/. The German version of Samuel is /zaːmueːl/, so if I'd try to make a short version of the German Samuel I'd use /zam/ but that sounds very, very weird to my ears. Instead I'd probably pronounce it like /sɛm/, which is the German attempt to imitate /sæm/.