I think the word “cheat” has a positive and negative aspect.
The negative aspect (for keto) is greater than the negative aspect for a calories in / calories out mindset. For that mindset, the Sunday extra calorie day is just that, one blown day (“I’ll be back to it on Monday”). For keto - I feel that the effects are longer lasting in two ways. First, if you are in the beginning of your keto journey, you’ve just messed with your hormones (assuming some amount of carbs) and so maybe not just a single day lost on getting to fat adapted (maybe the low ketone measurements happen for several days). Second, you are back to reinforcing what many appreciate goes away after getting into deep ketosis. (Again, assuming it was carbs) You are avoiding what I have read here many times - that the urge for carbs and sweet things disappears over time (which I see as a true benefit of this WOE).
But, there is the positive side, you are signaling to others that their restaurant choice is not limited on that day. Imagine a weekend away in some exotic place where, next to your hotel there is a famous French restaurant with a fixed price $150 per seat menu that would be both a great multi-hour journey in flavor as well as romance for you and your partner (and the town has nothing else to do).
Does you partner want to hear “cheat day” or “you can go alone, I’ll grab some sausage at the market and make use of the microwave in our hotel room”?