I don’t think so, because in the first clip, Jack said the effects of eating the mushroom (i.e. becoming tiny) were only temporary. I think “that witch” must be Cora, because she is the Queen of Hearts. She lived in Wonderland, which is that “far off land” where these mushrooms grow, and so Cora could’ve easily brought them with her on her journey. Also, Jack is dead, as we saw her skeleton in 2×6.
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"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy