MBP16 charging: After sleep mode no charging (but with charging icon), restart helps
Apple hardware on 10.15.5 doesn’t charge batteries until they fall below a band so that they don’t always use a charge event when you’re mostly full.
This is intentional and documented fairly well.

https://support.apple.com/en-us/HT211094

This appears to be entirely correct behavior unless I missed something major in your question. This feature is excellent in my testing and I strongly urge everyone to keep it enabled if they want their batteries to last as long as possible before they get exhausted and must be replaced.