From the spec "For input elements without a defined input activation behavior, but to which these events apply, and for which the user interface involves an explicit commit action but no intermediate manipulation, then any time the user commits a change to the element's value, the user agent must queue a task to first fire an event named input at the input element, with the bubbles attribute initialized to true, and then fire an event named change at the input element, with the bubbles attribute initialized to true." But here there isn't any change here. If you want a spec change, file a spec bug https://whatwg.org/newbug Once there is a spec change, we could change Gecko's behavior.
Bug 1569596 Comment 7 Edit History
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From the spec "For input elements without a defined input activation behavior, but to which these events apply, and for which the user interface involves an explicit commit action but no intermediate manipulation, then any time the user commits a change to the element's value, the user agent must queue a task to first fire an event named input at the input element, with the bubbles attribute initialized to true, and then fire an event named change at the input element, with the bubbles attribute initialized to true." But here there isn't any change here. If you want a spec (https://html.spec.whatwg.org/) change, file a spec bug https://whatwg.org/newbug Once there is a spec change, we could change Gecko's behavior.