Cartels and price-fixing agreements are extremely lucrative, which is why they were commonplace until outlawed by antitrust legislation, and why cartels like OPEC still operate today. Unions and collective bargaining are no different. Unions are equivalent to a cartel of labor-suppliers, and collective bargaining is identical to price-fixing.
Just like with cartels and price-fixing agreements, unionizing would likely benefit the average tech worker. It would also have an extremely bad effect on innovation, bureaucracy, and cost-of-tech-development which would spill over to consumers in the form of higher prices.
I'm in favor of breaking up big corporations, as well as implementing a wealth tax, raising the top tax rates, and strengthening the social safety net. But I don't think encouraging the formation of cartels and price-fixing agreements is in society's best interests.