Tyre size variation for the same size

Is it generally accepted that there is some small variation between tyres of the same size. My road bike has been stated (while searching forums) that it has a maximum tyre size of 700x28mm but on trying such a tyre it just touches both front and rear so unusable. Luckily I have another bike I can use the tyres but just wondered if this is pretty much normal as tyres vary slightly in size. It's not the width of the tyre that is the issue it is the actual depth which is too tall for the dual pivot brakes so I guess while the size is officially 700 it is effectively a bit more than that maybe 705 or 710. I think I'm right in saying the 700 is an outer diameter measurement but clearly there is some variation here as the tyres get wider the diameter also increases. Is this measurement available for tyres maybe as a depth figure? I just wondered if there is some way of checking before hand the height of the tyre that is too big (Kenda) with another brand to see if I can actually fit a different 700x28 tyre. I have bought 700x25 for now but really wanted to use 700x28.

These are the tyres that don't fit.

https://www.planetx.co.uk/i/q/TYKENK...00c-wired-tyre

They were actually £3 each when I bought mine so not exactly a huge investment but I've always found Kenda tyres excellent with strong sidewalls.