sure, i did in my late 20s. i can't really speak to the union aspect of things, but i never regretted picking up additional trade skills, or just skills/experience in general.

i think narrow skill specialization is a shit deal that is sold to laborers a lot more frequently than employers actually want it. like maybe if you're one of the like 100 neonatal cardiologists or whatever that exist in a nation... yeah, you can write your own ticket... but most labor need is finding people who can do a decent job and not be a liability. unions under capitalism use collective power to resist this, but without a revolutionary reordering of society and the power structure, it's a losing game.

maybe the pure specialist path works when society is stable, but in my experience as a multi-talent generalist, i have more options when the landscape shifts. and all it seems to do is shift lately. when i couldn't find full time, i could cobble together odd shit and charge rates based on what skills were needed to get by while i plotted my next move. when i was pissed at an employer, i could cast a broader net for the next opportunity to apply to. it certainly sucked starting over as a bozo that first time, in terms of shit pay and professional respect (zero), but it gave me the opportunity to try something completely new that i had curiosity about. exploring that new passion mentally reset me, burnout wise. i looked forward to the new work and digging in.

also, and it's more of a bonus, but acquiring new skills and knowledge dramatically increase the potential for making profound leaps of understanding, those genius-type moves aka "making connections across disciplines", where you take an understanding from one area and use it to solve a problem in a second area. the single-skill specialists, no matter how talented they are, are limited in their thinking. deep understanding in a single field allows for fast moving solutions, but it also comes with a rigidity. fields are always changing, and the deep specialist can have a harder time adapting to those changes.