Using the default startup values of variables as a "save your butt" system is not good enough in my experience. The coder needs to apply way more rigor to the development process than to accept he/she will be saved by default zero values.

I absolutely that to depend on anything to "save your butt" is wrong, but if your startup code explicitly (and as verified by you) makes a given variabl a given value it is not "depending on" it is "the code does". Of course the original post and its reason for in some cases working is an example of "depending on" and, as such wrong.

does your code start
SFR1 = SFR1default;
U8 var1 = 0;
U16 var2 = 0:
....

I doubt it

Erik