from the article:

“Starbucks gives autonomy to local leaders to ‘find ways to celebrate.’ These leaders are the same ones issuing many of the Pride bans,” it said pointing to an article that Pride decor was banned from about 100 locations across parts of Oklahoma, Arkansas and Missouri. Those locations are in some of the more conservative regions of a deeply divided United States. Many Starbucks locations across the country have been displaying Pride decorations.

Starbucks Workers United says this is an example of Starbucks bowing to pressure, as Target did when moving or removing Pride merchandise from some stores. Pride has become a political flashpoint this year, with the right attacking companies for celebrating the inclusive celebrations.

So these workers are striking against policies enacted by their local owner rather than solely for issues with a corporate policy (though surely they have reason to strike against corporate, too, and even the end of the article mentions Starbucks’ anti-union history).