BGP Synchronization

Hi Rene, i am confused to understanding this concept. please help.

So what I could figure-out so far is :-

"In a transit AS scenario, Enabling BGP sync made sense. because otherwise our ASBR router will advertise EBGP routes (learned from EBGP neighbor) to other internal routers as well and ultimately may become a transit AS for both EBGP neighbors which we don’t want.

So the rule said if we learn a route from IGP then only we should advertise it to other EBGP neighbor. that means we are only advertising network that we own.
But now this rule is not needed in today’s scenario. …why ?(please help me in understanding)