Why did Apple remove the ability to change fonts and enable night mode in ePubs created in IBA?

Re: "About ePubs created with iBooks Author - Apple Support"

I want to use IBA to create ePubs that take advantage of ALL of iBooks features. However, according to the above article, this is not an option: "you won't be able to change fonts or view ePubs created with these new templates in night mode."

I use night mode all the time, and I often want to adjust the size or style of font, so I'd like these options to be available in the ePubs I create. I also don't want to lose the ability to use iBooks Study Cards and Notes Panel features.

I already tried the iBooks format, but these abilities are also not there, since iBooks are made to be formatted a particular way and not changed much. That's why I'm settling for ePub format.

Is there a way to create ePubs in IBA that actually can take advantage of ALL of iBooks features?

DLM