Applied for a UK visa as a family, but received status on only one applicant. Is this common? [closed]

We applied for a standard visitor visa for the UK as a family of 4. Today I got back my passport with the Visa approved - I am the primary applicant. But we didn't get the other 3 passports. For mine also, I am yet to get an email from UKVI saying that a decision has been reached on my application. I just got a message from VFS to go and collect my passport.

At the VFS center, the lady showed me the status for the other 3 passports - it said something like "Outscan from Embassy to VFS". Mine was "Inscan at VFS" indicating it had been received.

Is this a common happening? Does it mean only their passport dispatch has been delayed and maybe arriving later in a few days?

Or could it be possible that the applications are being processed separately by different ECO's on their individual merit? I thought that a family visa application with the GWF numbers tying them together would be considered and processed as one. Is there a cause for concern with the other Visa applications?