yes its all true remember they have been together for millions of years helping each other .

yes up to a point. In the open ground that is certainly true as the worms create gaps in the soil that allows roots space to grow.
however in pots that isn't the case. there will be a point when there is more root than space, even in large pots.

yes that's right but only because pots are a man made unnatural situation .

That would only apply in heavy clay soil though - in lighter ground the pants would not get root bound anyway. I've never had a plant get root bound in the garden, only in pots.

Three ways to keep plants from getting root-bound when planted in heavy clay soil:
Prune circling roots when planting, and some of the top to compensate--especially in areas with low humidity, i.e., anywhere west of the Pecos River.
Dig generously wide planting holes--none of that soil auger business that cheap landscapers get up to!--and rip the sides of the hole with a cultivator to provide lots of nooks and crannies to trap circling roots.
Mix organic matter into the backfill soil--especially in areas with poor soil--and/or lay a couple of inches of organic mulch on the soil surface to encourage earthworms. Earthworms help aerate the soil, and leave channels for developing roots to spread through.

Couldn't think why Snoop, until I read it again...but its still true that mine have never got root bound in the garden...lol.

they wouldn't in the ground sg .