Have you seen how long this setup takes before it'll trigger a change? Ive left glasses of frozen water to thaw and they most definitely don't thaw evenly. They also take way more time to thaw than any regular food product due to the significant heat/surface area ratio difference.

I wish my freezer wuld have spare space for mug filled with water

I keep my freezer at least 90-95% (you may think 5-10% is enough for cup, but it's just small flat space available among drawers) full pretty much all the time, it keeps it running at highest efficiency and also you have always maximum available amount of food in case of lockdown for instance

Are you sure that will drop the moment the water thaws?

(https://www.usmint.gov/learn/educators/lesson-spotlight/make...)

Wouldn't the pressure from the penny bias your observatios from the mug?