Feral cats are usually pretty easy to distinguish. They’re often in poor condition; skinny, dull coats. They have outbreaks of cat flu when numbers build up, with gross mucus around their eyes, and they are mostly wildtype tabby. You know you have a problem when you start seeing them frequently stalking through the hedges and you start seeing the same cat causing trouble. They shit in the hay barns and cause toxoplasmosis-induced abortions in sheep and humans, not to mention the catastrophic impact on native birds. They need to be controlled. Taking every feral cat in to see if they are chipped is really not an option practically, financially or sensibly.
Even so, mistakes are possible, but if at any point they directly start attacking livestock, like chickens, it really doesn’t matter if they are a pet or not. That’s the outcome for any animal hassling livestock, including dogs, and it doesn’t matter a jot if they are someone’s pet.
Counting calories/macros is good thing to do to zero your brain in on what foods contribute what - it’s honestly quite surprising and informative to do. But, doing it constantly is kinda obsessive and annoying. Same applies here too.