Is it acceptable to create navigation and action bars with the same look and feel for the purpose of creating consistent UI? [duplicate]

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I'm new to iOS development. I understand that Apple provides APIs to customize the navigation bar, but I'm using Xamarin to create a cross-platform app. On iOS and Android, the navigation and action bars do not look the same as both platforms have different UI conventions. However, I've been feeling increasingly tempted to create consistent UI as opposed to native experience. Google must have thought the same for their own apps and ported Material to iOS.

Having said that, it feels easier to just create a Grid or StakLayout and use it as the navigation bar for both apps. The question is, do developers already do this? Will Apple reject my app because I created a "fake" navigation bar so to speak instead of using what they already provide. The same question holds for Android as well.

P.S. Another reason I want to use a layout is so I can animate it easily.