Indeed. The link above fleshes that out somewhat.
Consider the “water heater” on a small scale though as a kettle. A small “instantaneous water heater”. In order to justify the insulation required to make a “keep warm”, or near-boiling, tank (in this case a small one) more efficient it needs to be “cheaper” than electrical/heat generation.
Physics dictates that heat loss is harder to prevent the smaller the volume. The bigger the tank, the more efficient it can be. On a practical level, at some point (small volume) you’re fighting an uphill battle against heat loss and “instant” heat starts to win. Sufficient insulation becomes too expensive.
An idealized fridge/freezer should definitely be dumping heat into water and heating it (at least in summer): a fridge should dispense hot water! That pretty much embodies the difficulty with the calculus. Manufacturers end up making things that sell that are certainly not ideal.
Kettle calibration: On the smallest of scales I’ve found that Sense has helped me to innately calibrate my ability to fill the kettle to just the right amount without wasting any excess hot water, and most importantly without fiddling with, say, filling a single cup and then pouring it into the kettle to heat. Efficient laziness.