Question about rare ore spawns

Greetings, capsuleers.

I’ve been playing this game for quite a while but for the time being I didn’t touch mining properly (so not talking about Venture event mining and occasional Ice scraping for some fuel components for fun).

But a few weeks ago I decided to explore this side of EVE and I’m starting to have questions. Some lowsec ore anomalies (as per new map) have also a chance to spawn in high sec systems. But not in all bordering ones. Is it a map bug that shows spawn possibility in 0.5 systems? And why only some (red line) 0.5 systems show possibility of spawn but not other similar (blue line)?
What is the difference between these systems?