Yes, but it's not recommended - it does not have inter-frame compression, so it is significantly less efficient than just having a regular video file and slapping 'gif' on it.
That's not strictly correct, it's rather that the current encoder does no inter-frame compression. Patches (and the frame system in general) does give tools to do some inter-frame compression (not as many as in video, but still quite expressive), just nobody stepped up to implement compression using them for animations yet.
Do you know of a video format that supports progressive decoding?
Progressive decoding isn't a very useful video feature because you need to decode the whole frame before you decode the next frame for inter-frame coding methods anyway.
It is, however, a very useful image format feature, giving you most information from the spinner/sticker/emoji/sprite, and refinig the already playing loop as it loads. That's why animated jxl is a bad video format — it's not a video format, it is a separate kind of seemingly weird thing.