I'm with Malone on this. The letter in row 10 is checked with the down entry so can't be included - if these shared theme letters counted as unchecked we'd have 4 S's instead of the 2 shown in A dark hill ......
Thanks, Brendan. I felt my logic was quite sound, but I am not always sure of the terminology ('unchecked', say). I didn't do anything, didn't tick anything off, with the 'A Dark Hill..,' letters - more through laziness than arrogance!