Just a tooltip error.
Shield battery suppose to restore 36 shield/second on normal speed, 50.4 on faster speed, and 21.6 on slower speed, but they forget to sync the number according to game speed.
If you create a new game with slower speed, or slow, normal and fast speed, you will find that the Battery always shows restore 36 shield per second regardless game speed.
Immortal’s attack speed tooltip is correct which shows 2.42 and slower speed, 1.45 at normal, and 1.04 at faster speed.
A tooltip error is still an error that need to fix anyway.
Edit: actually I reported this bug on June, but it seems they ignored it: