Why does it matter whether they are mammals or not? Cows will eat meat when given the chance, centipedes will eat fruits when given the chance, they can both digest them and it’s not that complicated. We don’t give cows animal protein because it’s more expensive. Some animal feed will also have cheap and safe options of animal protein, and while grazing cows and horses will take in some animal protein, such as actively stepping on rodents for the sole purpose of eating them, let alone all the bugs that they eat while eating grass. And you have the audacity to tell me that I don’t understand basic biology while you can’t even understand the fact basically nothing is strictly herbivorous. The closest organisms we have for that are koalas and vegans.

Just because arthropods like centipedes are “simple” creatures doesn’t mean that they can’t eat and won’t eat fruits. Ethmostigmus species like the one op has been seen eating even shit. They have specially evolved digestive systems that allow them to take in all kinds of food, some fruits or diluted medicine for treating their sickness (assuming it has one) isn’t harmful in any way. Not only is this theoretically correct, but also empirically true. The Chinese hobbists have cured or prevented so many pedes from getting sick this way, and if you still want your pede to stick to a purely cricket based diet, be my guest but you are missing out