iPad Mini Split Screen question

Do I understand it correctly that I cannot split the screen 50/50 in “portrait mode”?
Attached a picture of the feature from my phone
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Does anyone have any experience using the 25-75 split?
I am thinking of mounting an iPad mini as the main device in my car, so I want to be able to control media(music or podcast) as well as see navigation instructions.
https://preview.redd.it/sn6mdkpwsrd51.jpg?width=621&format=pjpg&auto=webp&s=8687cc5c88182143dd15aa7903f6b00b110b8694
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