Some tech specs for using porotherm, with regards to UK, NZ building regs, page-119

yes, much of what you describe are certainly probable problems that need to be overcome.
the per unit cost will be lower.... but then how many required to match the laying speed of the HX.

many of them working together from what i read wouldn't be a problem. There are many examples of robots/AI working together in a group/swarm to solve problems, achieve a goal.

power source is an issue. absoluty tethered with power cables wouldn't work.

on the plus side, the same base model construction robot with different attachments/hands etc could allow for a lot of flexibility on building sites.
if one breaks in a team of ten on a building site for example, just get another one delivered, get the broken one repaired.... no disruption to the build.

they are thinner, but can already carry 18 kg blocks/boxes. slower yes.....

it is the classic problem of.... do you have a single large specialised machine like the HX on site..... or do you have many smaller robots that can be less specialised from a hardware point of view, while being more adaptable to do a wider range of tasks.