.NET MAUI, like Xamarin.Forms, uses by design platform native controls under the hood. This means that components like entries, buttons etc. are actually converted in their Android and iOS equivalents.
Therefore the default version of entry will be different in iOS and Android.
You can use handlers to make them as similar as possible, but if your main requirement is to obtain two apps which are perfectly identical on both Android and iOS, maybe you should choose a framework which doesn't use native controls, but renders all from scratch.