Does it? I think it should treat everything as a string since it can't be certain about the correct type. It could also suggest the correct type rather than applying it without user confirmation.
Looking forward to the first time anyone tries to use your excel on a table of numbers and then immediately has to multiply everything by *1 (in a separate table) just to get it back into numbers...
At least you would know what's happening and be in control of it
"Hey, is that a date? I bet that's a date!" - Aaaargh Noooo!