I would assume that the author of the sign chose that spelling because that's how the words sounds and she didn't know the standard spelling, not because she was relying on established historical spelling.
This is why I still don't agree with people using the word orientate. It may be a valid word, but they're not using it because they know it's a valid word. They're using it because they're back-forming it from orientation.
I don't think those things are mutually exclusive. Back-formation is a valid way to form words, sort of like how
back-form is back-formed from
back-formation.
And I disagree about people's motivations. Most people have no idea about morphological processes, at least not consciously. People use words because they hear them being used, not because they've studied the processes for word formation in Latin and English.
And anyway, it's not clear that it's a back-formation as opposed to a regular derivation of
orient +
-ate. I think the original reason why it became a prescriptivist bugbear in the US is that we've developed this notion that if we have two words that mean the same thing and have similar forms, but one has more syllables, then the longer one must be wrong.
