That is the most likely explanation - Its interesting scanning systems discovered/explored by older technology, as there is still a lot of valuable planets undiscovered and mapped.
I am currently doing a little shakedown of my new Mandalay about 3-4k ly from the bubble. I'm finding systems that have not been fully scanned, from the pre Exo and SCO days. Previously CMDR's might not bother with planets and moons that now have Exo data or systems orbiting stars that took too long to visit, but are easily in reach of an SCO equipped ship.
Could be a rewarding way for those CMDR's new to exploration to find undiscovered planets without travelling too far from home.
Safe travels CMDR's 07