Agree to an extent but there is inevitably some overlap between trades. You wouldn't call in a chippie every time you needed to notch a joist. You'd just learn the requirements for safe / permissible notching.
Likewise, as plumbers / heating installers we should be able to install a shower or heating controls , or to move a fused spur without calling in a spark.
However, as electrics are notifiable, I see the need for things like the "defined scope part P" which allows you to self-certify minor works without being fully 17th Ed. qualified. As long as people don't think that makes them a sparkie, and as you say, are big enough to know the limit of their competence, it's better to have these training schemes than for people to just bodge it.