Looking at the picture only, are you sure there was not a heating control on that wall where the temporary junction box is?
I only ask due to the cable capping being cut so well, height of it, spacing of it, location of it, the holes in the wall are the same shape/size of a back box fitting. Also why did your electrician start taking off plaster at that point and not at the holes you have drilled level to the shelving brackets?
Cable faults via drilling through plaster we normally look at the point where it was drilled, not a foot above it? Then we repair it where it is damaged using different methods suitable to the fault. Never seen a "drilling fault" fixed by randomly taking off plaster a foot above and installing a junction box??