There are some differences as you said. If you're an auto factory that goes on strike, the management is likely still making money—they have all the cars made yesterday and the day before to sell. Of course, the pressure would rise much quicker in a factory vs a tech company; where the latter could presumably float itself for a few weeks, the former would start losing money within days.
I'm sure whenever I get a new job and resign they're going to be like 'oh shit', because there's just not anyone left to replace what I do, really (I'm the last person in the department with a good amount of knowledge on their proprietary and stupid complicated phone systems, and they've kept me too swamped to be able to do any knowledge transfer worth a damn).
And in phone systems, there's always something going wrong or down, it seems like, often network related.
You're mistaken in thinking that a walkout is the only, or even primary, method of direct action organized collectives can employ.
Here are 197 others: https://www.aeinstein.org/nonviolentaction/198-methods-of-no...
Certain types of work-to-rule (https://en.wikipedia.org/wiki/Work-to-rule) would bring most tech companies to their knees in a matter of minutes. It wouldn't just gum up the works as it would in industry, it could literally put systems into failure states.