causes an error "XML error at start of text - orphaned data" - I'm just wondering if that initial tag shouldn't be supported when processing apl-to-array...
You are correct; that is expected to work. The message indicates that ⎕XML believes that the first element of the right argument character vector is neither a space or '<'. You could establish whether this is the case by passing your XML text to ⎕UCS and checking that you get 60 as the first element in the result.
If you are reading the XML from a file using ⎕NREAD etc, it is possible there may have been a Byte Order Mark (BOM) at the start of the file which you have imported.
If ⎕UCS either does show the expected 60 in the first element, or does not and it is not clear why, then please send me a workspace via Support and I'll see if I can determine what's going on for you.