A ring is preferred as the floating anchor point on the bridge of a tree climbing harness because it is round! Roundness results in randomly spread wear over the connection point. That is, wear is not concentrated in one place on the connecting aluminum ring.
Drew Bristow was well aware of the ring-on-the-bridge benefits when he attached the new DMM Bat XS rigging hub to his Treemotion harness back in March. But the alluring features of the DMM XS were just too hard to resist - a textile friendly, 'multi-port' on the bridge.
Now, six months later the logic of the ring is more obvious. The large hole on the Bat XS plate has worn at three points, in direct correlation with the three connecting holes opposite the large hole. As you would expect all the wear is concentrated at these points and not spread randomly (as you get with the ring) - this is not rocket science but interesting never-the-less.
Hamish Fraser also runs a DMM Bat XS on his Treemotion using Donaghys Armor-Prus 10mm as the rope bridge (naughty, naughty). Hamish observed a startling decline in the Armor-Prus 10mm over a period of a week following initial recognition of wear on the bridge.
The rapid decline might be due to the torsion applied via the use of the three connecting points on the DMM Bat XS but that logic is subjective. Hamish's plate wore in exactly the same places as Drew's - see image below.
Care should be taken when using equipment not designed specifically for the purpose in which it is finally used.
This is not to say there is a problem with the DMM Bat XS - just be careful where it is put to use. If you are using one as a 'multi-port' on your rope bridge please be vigilant for wear and change the bridge (and DMM Bat XS) if you have any doubts whatsoever.