A "competitive advantage in the capital market" means something that VCs require from the companies they invest in, like "strong founder team" and "established product market fit". I don't see a lot of VCs demanding or preferring unionization among the companies that they invest in. Do you know of many VCs that have pro-union stances? Even if there are some, I think it's fair to say they're not the majority, hence it's likely a unionized business will not have as good of a capital-raising opportunity as a non-unionized business.
> it's likely a unionized business will not have as good of a capital-raising opportunity as a non-unionized business
I think a huge factor in this is that there are zero unionized businesses around in general. Chances of any of them being invested in by VC is therefore similarly zero.
If some marginally popular company unionizes, everyone will see that it’s not the big deal they make it out to be.