I'd agree with you, IF IT DIDNT CLOSE DURING THE SEASON!!
If it operated until the last day of the Season, that'd make sense, but they decided to close it randomly one day without giving out a proper hint on it outside of s chalk board on the ride that was stupidly vague. Guests would've wanted do ride Duel in scarecrow for obvious reasons, but nope, they can't, and no one knows why. When I went this scarefest, every guest in the area excluding 2-5 didn't even knew it was shut and were really disappointed and were slightly angry thar they weren't even told or why it shut.
That's not a reaction you wanna get from your Guests tower's.
I'm not sure that necessarily makes any difference.
The Flume closed permanently on 10th October 2015, so the entirety of Scarefest was still to come at that point. The park did say that it was "closing for the season"... but that implied that it was reopening in 2016, and there was no acknowledgement of its permanent removal from the park until February 2016.
Toyland Tours closed in June, so the whole summer season and Halloween were still ahead of it. From what I can gather, Alton Towers did not announce that one either, and I'd argue that CATCF was a pretty drastic metamorphosis, with a radically different theme being applied and a whole new separate ride system being bolted onto the end.
In fact, I'd actually argue that the mid-season closure makes it
more likely to be a bigger redevelopment, if anything. If it were a smaller one with most things being kept the same, surely they could have contained it to the closed season, no? The conversion from The Haunted House to Duel was done entirely in the closed season, for some idea, and that involved demolishing and replacing a not insignificant portion of the ride, refurbishing the remaining HH scenes, and fitting a brand new interactive blaster system.
Given Towers' reliability woes this season with the likes of Hex and Enterprise, I'm sure they wouldn't have shut Duel in September unless they absolutely needed to.