From a societal standpoint, it doesn't particularly aid widespread inequality if a small number of tech workers receive a bump in income; the union may cause the situation to worsen, as the union has an incentive to keep the supply of employees restricted in order to maximize their compensation. The unionized employees would be protected from public competition.
Having pro-sports players in a union hasn't exactly improved widespread inequality.
Moreover, much wealth (especially at the top) is held in equities, often that aren't sold before being passed on to inheritance. That means:
a. that this wealth isn't counted as income
b. that decreases in equity prices due to unionization (and corresponding decreased expected returns to owners/shareholders) will burden the non-working rich disproportionately.
Sure, it won't solve wealth inequality - but where there is a zero-sum tradeoff, that tradeoff will mostly be from rich tech owners + management to affluent tech workers, not from the rest of society to the tech workers.
[0]: https://www.washingtonpost.com/us-policy/2019/02/06/people-l...
Similarly in tech, unions can be a way of gaining greater profit sharing for the high-skilled workers necessary for the business to function. Where tech workers lie in income percentile is irrelevant and distracting to this question.