Yes,it true.Before you change your status from Single to Relationship Facebook knows about it.
If you are looking for your dear ones in social network sites
just staring at their post or photos,same way liking their post and commenting on it , Where all things analyzed by social network sites (Facebook).
From their first meet and to the date everything has been analyzed and this data is supplied to various studies (University Level) .
Single persons before they have touch with their partner they are more active in social networks,They are most largely spending times in surfing their loved ones profile.A study says average 56 seconds were spend per day on this.
This includes Staring at their Profile,Like,Message,Comment and Chat. They are more active and want to know about each other at the starting time.More feeds were uploaded by these persons when compare to others
During relationship, After they confirm and their need have been satisfied by social network.
They start to reduce their activity in social network site.....they do this process within few days after they fell into affair (Relationship),They come out from invisible world to reality.They start physical activities by avoiding social network contacts with each other and all of sudden they disappear from being online in social networks for weeks and months...,
After few days they Post about their relationship in Social network,Probably Date Picture,Marriage Picture,Child Picture .Mostly with ♥ (Heart Emoji's) they post as they are in relationship.
Few suggest they Leave/Offline/Reduce Posts in social network because of partners warning .After relationship starts people avoid social network activities and concentrate in family activities and use those sites only for contacting friends,Emergency needs and Supply.Their other activities in normal life make them away from social network sites (Facebook,Twitter,Google Plus)