Going back on the project itself, I recently reached our to a few people on LinkedIn to ask about the apparent construction delays. I won't disclose names, as per their request, but all three of them gave me the same answer, in different ways: the project is on track to be finished on time and should be done by the end of Spring 2022, the first stage of the construction was very sensitive (as someone pointed here) as there was a risk of damaging the (very expensive) acoustic isolation infrastructure in the existing building with vibrations from drilling and settling the foundations. According to one of them, now that this stage is essentially done, most of it is glass and steel, with some concrete pouring, but we should see it rise fairly quickly in the next few months.
I also asked if there had been any sort of changes in the final design (ie. value engineering) and the answer, from all three, was a resounding no. Which is also one of the reasons they haven't sped up construction, as the architect is very adamant and considers this project one of his crown jewels.