ClearAll required twice on a symbol with SyntaxInformation

Question

SyntaxInformation[f] = {"ArgumentsPattern" -> {}};
f[] := 0;

After one ClearAll[f] or ClearAll["`*"], f remains black. It takes two to turn f blue, and it can't be in the same cell: just running ClearAll[f];ClearAll[f] is not enough. Yet one ClearAll is enough to clear FullDefinition[f].
In fact, the line f[] := 0; is extraneous; all that's needed is to define SyntaxInformation[f].
Is this a bug? Is there anything I can run once to turn everything blue?

Blrp · Accepted Answer

It's a bug. From Wolfram Technical Support: "I have reproduced the issue and have reported it to our developers."
Workaround, from the comments by Lukas Lang: SyntaxInformation[f]=.; ClearAll[f] or Quiet[Unset@*SyntaxInformation@*Symbol /@ Names["`*"]]; ClearAll["`*"].

ClearAll required twice on a symbol with SyntaxInformation

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