Stock options are offered to people who are ready, willing and able to work harder or smarter in response to potential ownership. These are INDIVIDUAL contributions.

When a direct relationship exists between the parties, this is a possibility. When there is a third party dictating what happens, this is much less realistic.

Tesla is a publicly traded company. It's relatively easy to put a market value on their stock options.

> [...] because otherwise they could be demanding something more valuable?

Like twice as many stock options? I'm a bit confused. Stock options are fungible. You can make granting of stock options worth arbitrary many dollars, by eg increasing the volume or lowering the strike price etc.

Just a guess but union contracts typically fix compensation for a given role and seniority. So every role would get the same number of options. Not having control over how many options are granted (linking to performance) may mean the company doesn’t have much incentive to grant them to union members.