The battery icon is not a reliable indicator until after logging in and reaching the Desktop. Thanks so much Apple for not properly testing the basics yet again.
It is very hard to determine the true health/condition of an Apple battery. You can try running the Apple Diagnostics to see if any hardware issues are detected. If the diagnostic reports a problem, then you should have Apple or an AASP examine the laptop and repair it. However, a passing diagnostic result does not necessarily mean the battery (or other hardware) is healthy. I've encountered lots of Apple batteries which tested fine, but through other means of testing and monitoring I've discovered a hardware fault with the battery.
As for the red battery icon on the screen indicating to connect the charger, this seems to be a common issue with our organization's Macs. I'm starting to believe this is just "normal" behavior for these USB-C Apple laptops which may have been exasperated by a recent system firmware update (seems more common recently, but maybe this is just a coincidence). If it is a hardware issue, then it is an issue with the Logic Board since I've experienced the issue on laptops with a brand new Battery and an otherwise working laptop.
If the battery condition reported by macOS is "Service Recommended", then it indicates either the battery capacity has dropped below 80% of the original design capacity or macOS has detected a hardware fault with the battery. Coconut Battery can tell you whether the batteries current Full Charge Capacity is at or below 80% of Design Capacity (sometimes when the capacity is about 80% there can be some fluctuations a bit above or below which may have the "Service Recommended" condition change back to normal). If the battery's Full Charge Capacity is above 80%, then it may indicate a hardware issue with the Battery. As long as the Apple Diagnostic does not reveal a problem and as long as the battery is performing to your expectations, then just ignore the "Service Recommended" battery condition. Unfortunately a battery hardware issue may be intermittent and may only present itself at certain charge levels or perhaps only under heavy system load.
