Had the service battery come up on my MacBook Pro (13-inch, 2017, Four Thunderbolt 3 Ports) 10.15. Upgraded from 10.14 to the public beta of 10.15 then to the official release. Only noticed the service battery a week ago. Contacted Apple and they said I should see a genius at Apple store and booked an appointment. Was in the process of backing up everything before hand and decided to do a clean install of 10.15. Now the service battery has gone and says status is normal.
Health Information:
Cycle Count: 408
Condition: Normal
Have drained the battery to 0% and now charging it back up to 100% to see if anything changes.
I've still got AppleCare to June, 2020. So I'm not worried at the moment if the service battery reappears.
But I would suggest anyone getting the "service battery" and with little time on their warranty to get it looked at just in case.
If you are out of warranty then it might be worth doing a clean install of Mac OS or search the forum more and see if it is more common and perhaps a Mac OS patch will come out to fix the issue of false positives for "service battery"?