At the very least, collective assistance could be very useful at Google in negotiating fair compensation for new hires and in sustaining that fairness over time based on performance data.

After all, Google has huge quantities of data to let them decide on compensation, the employees have extremely little and unevenly distributed access to similar data, and it doesn't feel like there is much opportunity to recover lost wages if you realize you've been underpaid compared to peers (aside from discrimination on illegal grounds).

I presume the same would help at other tech companies.

None of this requires the stereotypical fossilized rigidity that give unions a bad name, and I wouldn't want that either. Even in the US NLRA system that's not at all required.