The law (in many places) gives protection to workers being laid off which it doesn't give to those being fired for inadequate performance. But when a company can change a target value and huge number of people are fired instead of being laid off people need to push back.

Is it any surprise, when the law creates an incentive like this for constructive dismissal, that constructive dismissal becomes the standard practice (even if it is supposed to be illegal)?

The results are the same: your company has one employee less and you have one employer less.

Big companies offer packages when laying people off, n weeks of full salary once you are gone with m weeks before of time to find a new role internally or externally. This does not happen when you are fired for cause.

Most people have a notice period so that’s normal. If you are ‘lucky’ you have garden leave so you can’t work/need to go to the office during this period

That was the most convoluted admission of ignorance.

Definitely it is big difference. In first you get fired without any reason. In second your manager is told to find any reason to fire your.