Again, it's not a dialect of bokmål. That would sound like bokmål is actually a spoken language and there are dialects of it. It is not. It's the other way around - bokmål is an attempt to create a written language with common elements for a lot of people, and the same was done for nynorsk - it's just that for bokmål the selection was more from certain city areas in the south, and nynorsk more from dialects elsewhere, but that's actually a too easy description. In my own dialect, which originates very far from where bokmål was created, there are tons of similarities but also tons of differences, and the same can be said for just about every dialect.

When teaching Norwegian to foreigners there's really only one practical way of doing that - use an artificial "spoken" bokmål so that the students can actually match speech to written words. That's just a crutch in order to learn the language (after you're done the real learning starts). That doesn't mean that "spoken" bokmål (or nynorsk for that matter) is real outside the learning institution.