I think if one qualifies under FSTP without any Canadian experience, their score can potentially be lower than if you qualify under CEC or FSWP. The minimum required CLB would be level 5 , which would only net you 24 out of the possible 136 points.
2 - 3 years of foreign experience (the minimum for FSTP) will give 25 points.
There is no minimum education requirement for FSTP, so one can technically get as low as 0 point for education.
Finally, one would have to be either certified, which will give an extra 50 points, or having an LMIA job offer (an extra 600 points under CRS) to qualify under FSTP.
In total, at the minimum, someone can either 99 points without LMIA, or 649 points with LMIA job offer under FSTP, so yeah, it's possible to have score in the range of 600s if you qualify under FSTP (let's say, if you are older than 45).
But then again, these people are the types of people that Canada is currently looking for. Their skills must have been transferable, else they would not be able to qualify under FSTP to begin with, and since most likely, only those with LMIA will get invited, they will get to contribute to the economy from day one, whereas those coming from overseas with scores in the range of 400s would still have to first find employment once here.
I am a PR, and it took me a while to find employment in software engineering, and that was after obtaining a Canadian credential. I share people's frustration here, but there is really no point in thinking that, i.e, someone in trades would be less of a contributing immigrant than white-collar workers.