cement actually preserves things pretty well for forensics.. I thought it was the city that was trying to fill it in and the jews were ripping up the wooden formwork in one of the videos to prevent the thing from being filled in.
$0.02
well that's the thing.. cement is generally porous.. if you had bodies decaying behind 12 ft of cement, it would still smell, and the decay could still be analyzed from whatever surface the smell was coming from.. so even when its done with discretion its not practical.. it became somewhat of a trope in television about mafia and secret agents etc.. but in actual practice, it hasn't shown to be nearly as effective as it's portrayed to be in the movies..
And so in this situation, when it's already a contested site by law enforcement.. a last ditch effort to cement it is pretty high profile stuff for something that would keep stinking for many months to come.
I watched something in the past 5 years where they referenced the failings of cement for hiding bodies.. feel like it was sopranos or some shit.. like they ditch a guy at a construction site, 6 ft under, but then they're all like "6ft, you can't do 6 ft! its cement not soil you fuggin moran" and the place stinks like hell, and they have to go back in the middle of the night with a jackhammer and move the body.. And it's because soil will actually hide the smell, but not cement.