Concrete/self-leveling compound around pipe connection to sewer stack??

[Bonae]

Hello!
I have advanced plans to move the kitchen (in a turn-of-the-century apartment) to the adjacent room. To make this a reality, certain rerouting of water and sewage is required. Naturally, I had thought of leaving this to a professional, but considering what a plumber charges, I would like to prepare as much as possible.
A problem that quickly became apparent is that the current sewage pipe connection to the main pipe seems to be embedded in some kind of concrete or thickened leveling compound - meaning it looks like the pipe connection was made and then a bucket of the stuff was poured into the joist space around the connection itself. Is it customary to do it this way?? I assume that to access and make a new connection, I would need to chip away the mass with all the hassle that entails? Is there a risk of damaging the pipes? That would really not be good... I do believe that a stambyte was done relatively recently, so there should be no risk that the mass around the pipes contains asbestos.
In the picture, you can see the main pipe going down into the mass I'm talking about. You can't see the sewage pipe here, only where it then protrudes through the floor under the sink. The above-ground branching is the neighbor's sewage coming in from the other side of the wall. Since the water pipes and sewage have been built into a small box in which I have cut an inspection hole, it's not possible to take a more comprehensive picture than this.