There is actually a post on it in the Known Issues thread, not by Devs, but by players.
Though @Saltypatra updated the known issues thread right after those posts, and it wasn’t added to the known issues list, suggesting it’s an intended change.
Also to compare the two here are my Zae’jin shots for PC and Mobile:
PC:
Mobile:
Using this as a reference:
We can see that the difference between 3 stars and 4 stars is 300 points. And I’m at 2160 on Mobile, which if you take away the total needed to get to 3 stars (2100) leaves me with 60 out of the 300 difference needed to get to 4 stars.