I think the action will have a tough case to prove. An article on another blog states that College Recruiter lost their traffic that then came back to College Recruiter after they added structured data. The way to get the ranking is to add this simple data structure to any site with a vacancy page so no barrier to entry.
If you know anything about SEO then the structured data should have been there in the first place and to tweak it for the GFJ format College Recruiters tech team would have needed to do 2-4 hours work max so where was the big issue? Smacks of a storm in a teacup to bad mouth Google? What you had to code and how was published to anyone who wanted to know (still is) about what data to set up and how.
Hard to prove for the two UK companies named, I did some testing and for two-word jobs searches they rarely appear in the top 100 results, so google cannot disrupt traffic they did not have from rankings they have yet to achieve. In fact, you can say if they just added structured data to their job posts they’d be better off on Google for jobs.
This action for me misses the real place to look and see if Google for jobs is anti-competitive if you enter the platform jobs are delivered in a questionable way for me, like the following examples.
Why is a job that is 10 days old on Total Jobs (an early adoption partner) ranked above a job 3 days old from a non-early adoption partner ranked 2nd?
Why are the penalties for how job titles requested as clean titles not being penalised on the early adoption partners adverts?
Why do the early adoption partners ads rarely state the postcode and street name and rank higher than non-adoption partners with that data fully completed?
If Google’s stated aim is to improve the job search then the job advert with a clean job title, no amber warnings and fully accurate data (in the UK people are putting England as the Region when it should be a county like say Kent, or Yorkshire etc) in all field not rank the highest?