Simply denying service.

If Starbucks workers go to work all day and serve every customer but Bob, that's not a strike or walkout. Those terms have real definitions.

That doesn't mean it isn't a union activity.

Seems like if the reason for it is within the law regulating worker action, it is, in fact, union activity, and is, in fact, a strike against Bob, according to some Nordic countries.

Is your sole problem with the fact that people are calling something a strike, and you personally don't think they should, according to your possibly single-country-centric view of the term, or is there a substantive objection?