What's the intended usage scenario of the Cat5e runs in my new house?
Summarizing what has been said in the comments:
Having the blue pair paralleled between all the cables strongly suggests the builders intent was that they be used for phones. Cat5e cable is often used for phone wiring as it's more interference resistant than regular phone wire and the blue pair is the conventional &quot;first pair&quot; for phone wiring.
As for your options, there are two main ways forward.
Option 1, ditch the phone wiring cut off the builders mess and terminate the cables individually as network cables with all four pairs. This will let you run gigabit networking.
Option 2, leave the phone wiring as it is and use the green and orange pairs of each cable for Ethernet, this will limit you to 100 megabits per second.