2018 Elantra Battery Issue - Auto Shops Disagree

Main Question

Does the 2018 Hyundai Elantra have a "smart charging" system that would make the alternator level appear high (15.1) and the battery level might appear low like 9 instead of 10.8 or 10.9? Two shops telling me two different things.

Details

2 months ago car wouldn't start. Auto repair shop A puts a new starter in. Week later car won't start again. Take it back and they test battery with carbon tester instead of digital and it reads really low. Replaces battery and says starter was never the issue.

Yesterday auto repair shop B while troubleshooting another issue (whine possibly from transmission) tests alternator and it is 15.1 which they say is high. Battery tested at 9 which they say is low. They don't pressure us at all to do anything with either one.

Took car back to auto repair shop A and they test everything and say alternator and battery are fine because they looked it up on their mechanics database and say, "this model has a smart charging system that will let the alternator get higher like that" and they said their 3 battery tests were all over 10. I asked if they used the carbon battery tester and they kept evading the answer and then finally said yes, so I can't confirm if they did or didn't.

Would appreciate any insight you can give because someone is either misinforming us or not knowledgeable. Thanks!