Bear in mind that once you open the package of Spam the pre-cooked element is no longer providing food safety. A better question would be: If I left an opened package of Spam at room temperature for a day, would bacteria grow on it. I'm guessing that the answer for that one is yes indeed.
I agree with your supposition, however I think the answer to your question is unlikely
Certainly your advice on proper food handling
is safer and perhaps in the backpacking environment the added risk of food poisoning is not worth it.
Overall the advice (from many respondents) to stay away from spam is something I agree with. I think there are much better "meat" options: pre-cooked bacon, hard salami, freeze dried meats. IMHO all taste better and are more shelf stable.