This is by design. Events from subscribed calendars don't appear in a user's freebusy information.

But this would be an integral requirement for handling resources with SOGo, right ? Or is this likely to remain as is ? If yes, then any tips how to go about this behavior ?

Also, the resource is an account, and free-busy information for that is retrieved when I try to add invitees. But, no conflict is shown.

As I understand this, you write your event directly into the calendar of the resource?

With this proceeding you are responsible for not overbooking yourself.
This is intended!
Only the "owners" of the resource should have write access to the resource in order to solve conflicts.

Automatic booking is only for users which invite the resource for their own events.

As an aside:
Why would a room or beamer host an event?

No feedback provided in years, closing.