@RobotimusPrime,
Where are you seeing this strength? and is you main Deco node also a Powerline Deco Node?
Signal Strengths should not be provided for wired connections, as wired connections are limited by their capabilities and technology, with their "strength" being labeled as a negotiated speed. You will, however, see a signal strength when looking at the device's powerline connection, or with a wireless backhaul.
I believe that in the case of Powerline Decos: the Ethernet and Powerline Backauls cannot work at the same time - only powerline and wireless backhuals may function simultaneously.
Are you seeing differences in speeds? or are they lower than what you are expecting?
If you perform a speed test while connected to the satellite node, what do you see for your connection?