This is embarrasing, but now that I look at the epub with the Calibre viewer and with Sigil, I see that the problem is really the Apple Books reader, not the ID export. That had never occurred to me; I did not step back far enough to think about the problem differently. In Sigil I see that the content.opf file has these lines,
and it appears that from the language specs that the Apple Books app decides to interpret the epub as an RTL book. The Calibre viewer and Kindle Preview 3 apps show the book correctly.
So there is no problem with ID export. My apologies for not looking more deeply into the problem before posting.
This is embarrasing, but now that I look at the epub with the Calibre viewer and with Sigil, I see that the problem is really the Apple Books reader, not the ID export. That had never occurred to me; I did not step back far enough to think about the problem differently. In Sigil I see that the content.opf file has these lines,
<dc:language>en-US</dc:language>
<dc:language>he-IL</dc:language>
and it appears that from the language specs that the Apple Books app decides to interpret the epub as an RTL book. The Calibre viewer and Kindle Preview 3 apps show the book correctly.
So there is no problem with ID export. My apologies for not looking more deeply into the problem before posting.