Since Eridians can have multiple soulsongs and Rocky also has Adrian's soulsong, does that mean Erid knows about Grace & the ocean-ship-thrum's plans to build their own expedition? Has Rocky warned Grace about space sickness?
This is my rough timeline of events, (*not to scale).
Yes, Eridians can have more than one soulsong. The terms I am using so far are:
Soulsong - a person who understands you on a fundamental level.
Chorus/Choir - a group of people/eridians who share a soulsong. Most commonly eridians find themself in a chorus of 3-6 members.
Sometimes a chorus has to be close, geographically, to hear one another. Sometimes they don't have to be. All members of the Blip-A were chosen because they had 'long-distance' choirs.
The canon events of PHM take place just outside of communication range of Erid. Rocky is too far from Adrian to sing with them- but beforehand the planet was warned that Space-Sickness was 100% totally a thing do not come out here unless you figure that out why people are dying in a horrific, slow, painful way.
This does change the trip back to Erid, because it's only about 18 months / 2 Years into the journey that Rocky and Adrian come back online to each other.
"Hey, honey! Look what I picked up! It's an eldritch horror! Anyway we figured out the sun problem we'll be home soon."