In the XSLT 3.0 spec at, https://www.w3.org/TR/xslt-30/ I can see a typo that perhaps needs to be corrected.

In the section, "15.3 Selecting the Sequences to be Merged" one of the lines of text says, "[ERR XTSE3195] If the for-each-item is present then the for-each-source, use-accumulators, and streamable attributes must both be absent."

The phrase "must both" seems wrong. There are actually three options.

Therefore, the corrected text can be, "[ERR XTSE3195] If the for-each-item is present then following three attributes for-each-source, use-accumulators, and streamable must be absent."

OR

"[ERR XTSE3195] If the for-each-item is present then the attributes for-each-source, use-accumulators, and streamable must be absent."