Happens all the time - hence the term "snowflake" babies. Although, I don't know if 8 years is a significant period of time, or not unusual in any way.
I thought snowflake babies were frozen embryos that were not to be used by the bio parents so other women would have them implanted rather than discarded. This embryo is biologically from Celine and her hubby. In fact, I remember when she was pregnant with her first many years ago she mentioned that there was another embryo and I always wondered if it would just remain frozen forever. Oh well, in any case it’s interesting that after eight years it has been implanted.