Multiple ‘Grounds’ help separate noise coupling
Separating grounds like and connecting them in a ‘star ground’ connection is NOT a good idea, especially when they joined to a star point by thin trace. Star grounding is a concept that was popular in the past when digital circuit was not fast. If you look at all the new schools of EMC, SIPI (Signal integrity + Power integrity), you will see no one recommends this method any more. Below is a snapshot of Daniel Beeker’s Altium presentation, in which he emphasised the importance of keeping one ground.
If you know what you are doing and if you layout the board very carefully, you can still split ground and make sure it is a pass. But most of the time, if not being careful, splitting ground cause problems. Check this. https://www.youtube.com/watch?v=g4YaSOKRklg