> In Germany now there are laws in place for this, you get ridiculous stuff like as consultant you are not allowed to eat together with team mates from the employer because that is seen as bounding activities
AFAIK in Germany the model of using temporary agency staff (AÜG or "staff leasing") is now tightly regulated. It works for a limited time period and tries to guarantee some equitable conditions for temporary workers like fair treatment, equitable wages, and benefits, aligning with the protections afforded to permanent employees.
Consultancy has no such protections.
I have never heard of any laws that prohibit internal employees from socializing with the externals (consultants or AÜG), or eat together. Bonding can happen equally at the desk or the lunch table. And I haven't heard of any company or institution enforcing this. Legislating who one is allowed to eat with sounds crazy.
What many companies probably enforce is "no internal benefits for consultants", so the free company coffee, parking, canteen, or maybe even a desk/office are not available for the externals, and they have to look elsewhere. Or maybe some unwritten internal rules to discourage bonding.