Tuplet tremolo question

I’m wondering how to notate this.

The time signature is 2/4. I start by setting 16ths and defining 12:8 in the tuplet popover. I can then enter two dotted quarters and there’s a brace with a 12 over it. So far so good. However, as soon as I call up the repeat popover and type 22 to get the 16th tremolo, Dorico replaces the dotted quarters with non dotted half notes instead of dotted halves. What’s the best way of achieving this?
tuplet tremolo.png

I can confirm that exact behavior, and I cannot find any good reason for this to behave like it does. Probably a bug.

According to Gould (page 219-220) this is the correct notation for single-note tuplet tremolos. Gould doesn’t give an example of a double-note tuplet tremolo but Dorico is following the same principle.

But I’ve seen it done like Vaughan’s example in old scores.

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