Voluntary TPR - how does that work?

Both of S's bioparents signed voluntary surrenders. In his case, when it became apparent that the court was going to move to TPR, the caseworkers and lawyers got together to explain to the bioparents (who were divorced, and so had two different representatives) that the kids had been in care for over two years with neither parent making any progress (one was in long term inpatient psychiatric and the other was living in a homeless shelter- after TWO YEARS of receiving RU services) Biodad agreed almost immediately to sign for the 5 kids who had preadoptive placements. The day of TPR the foster parents had to go to court too to sign "intent to adopt" documents, and biodad got the right to be notified if the adoption did not go through as planned. He did NOT sign the TPR for S on that day, as S was the only kid without an adoptive resource. Several months after that, after lots of preplacement work, S moved in with me. I then met biodad at court, was introduced to him as the woman who wanted to adopt his son, we chatted for 5 minutes, and he signed the TPR that day. He did not ask for any visits or updates on any of his kids. Biomom signed on all 6 kids a month or so later. She asked for visits to be written in- she is entitled to visits with the kids every 6 months. It is her responsibility to contact us and set them up, and if we feel it is not good for the health or wellbeing of the child at that time we can refuse. Also if she misses any visit, that part of the agreement is void. She also asked that all the adoptive parents sign that they will do what they can to maintain sibling contact. (All 6 siblings were adopted in the same county, but by 3 different families) I also have an acquaintence (a friend's sister) who had a similar experience- after her daughter had been in foster care for 2 years, she was approached about TPR and adoption, and told if she didn't sign TPR would probably happen anyway, and she would lose all chance at visits, but if she signed she woudl get to ask for visits, and she has continued to have visits with her biodaughter every 6 months since then.