I don't know if MM did or didn't intend for this. I would guess not, but I don't know that. If the description of the facility was "Only one per sector effective" then I would definetly say it was a bug and should not be exploited.
You can remote mine three planets with a single miner component. Is this a bug exploit? Was it intended? I don't know. I see it as the same thing.
This is different I think than a more obvious bug such as the mines per sector thing that is causing so many headaches lately. That is a little more cut and dried than this (although it's still a pain to try and enforce

).
Another example is the accelarted ship construction via retrofitting. Did MM intend for this to be allowed? A lot of people do it, a lot of people think it's cheating. It's a grey area. MM has addressed it a couple times. First in reducing the retrofit percentage to make it take longer, and making it more expensive. In the next patch there will be a prohibition against retrofitting to add a space yard or colony comp through retrofitting. All well and good, it won't be doable anymore. But does that mean anyone that did it before was cheating? I guess it depends on your point of view.
Geoschmo