Vedalken Shackles 
Artifact
You may choose not to untap this artifact during your untap step.
{2}, {T}: Gain control of target creature with power less than or equal to the number of Islands you control for as long as this artifact remains tapped.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
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$0.46#31083
"You may choose not to untap this artifact during your untap step."
+1 more matching line
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Entrancing Lyre 100%
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Tawnos's Weaponry 100%
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"You may choose not to untap this artifact during your untap step."
+1 more matching line
Deserter's Quarters 100%
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"You may choose not to untap this artifact during your untap step."
Endoskeleton 100%
$0.22#27874
"You may choose not to untap this artifact during your untap step."
+1 more matching line
Flowstone Armor 100%
$0.14#31381
"You may choose not to untap this artifact during your untap step."
+1 more matching line
Helm of Possession 100%
$5.07#14749
"You may choose not to untap this artifact during your untap step."
+1 more matching line
Elaborate Firecannon 95%
$0.05#28481
"This artifact doesn't untap during your untap step."
+1 more matching line