From the manual, Section 23.4.3 General Options:
Delete struck-through text Any text that has been struck-through in the output
will be stripped out of the compiled copy. If you use these marking
for editorial purposes, to “soft delete” text, this is the option to use to implement
those edits. When disabled (as it is by default), the text will be
formatted as struck-through text if the document type supports that form
of formatting. They will otherwise look like ordinary text in formats like
plain-text. <<
Based on the manual’s description, this option is supposed to do what its name indicates: Delete struck-through text.
You may want to email L&L support directly.
https://www.literatureandlatte.com/bug-reporting
Best,
Jim