The numbers after the “-” represent the package release number and are not relevant when comparing packages from different repositories. They describe the number of package rebuilds inside a given repository.
The relevant part here is the first one, the version number (1.0.28). For alsa-oss, there is no source difference – just compare this with this – but binary result may be different because the software used to build the package may be different. That’s why zypper dup forces the change to Tumbleweed packages.