Don't those workers working multiple 'full time' jobs usually have temp contracts paid by hour or service? I haven't seen a full-time contract that would allow

Don't those workers working multiple 'full time' jobs usually have temp contracts paid by hour or service? I haven't seen a full-time contract that would allow me to take other such commitments from other companies. Whereas when I was a freelancer I had to demonstrate that I have at least 3 roughly equal sized clients to be legally recognized as such.