Can you explain the difference? If I would want to get it over with, why wouldn't I send my kid to play with an infected friend?
Keeping young kids apart within the home is extremely difficult. Allowing them to play together is acknowledging that one can not reasonably keep them separated enough to make a difference. I am not talking about having them share plates, beds, etc. - just about not keeping them from being around one another. Generally, by the time one finds out that one child is infected, they have likely exposed their siblings.
Sending them to a friend or neighbor that they have NOT been exposed to is a different situation altogether.
In one, the parent is bowing to the inevitable - child A has Covid, and shares a room with B. They now both need to stay home, and keeping them apart would be very hard (to put it mildly. The parents can either make themselves crazy trying to keep the kids apart, likely only to find out next week that B also has Covid, or just let it go. B will either get or not get Covid (this time,), and if they get it, at least we are done with quarantining. I
In the other, they are deliberately sending their child to play with someone infected, thus intentionally bringing Covid into their home.