Hi aus9
... I wonder, is it possible for someone to accidently download the 32 variants....
Certainly, if they manually download extensions instead of using the intended tools (apps or tce-load).
... boot up on a 64 bit CPU and be none the wiser? ...
Since Tinycore does not support mixed 32/64 bit libraries (and extensions), no.
If you are running Corepure64 (64 bit kernel, 64 bit apps) a 32 bit program will fail to run.
If you are running Core64 (64 bit kernel, 32 bit apps), you can only run 32 bit programs.
If you are running Core (32 bit kernel, 32 bit apps), you can only run 32 bit programs.
I am aware I am on the correct variant as "uname -r" tells me so.
That only tells you if you are running a 32 or 64 bit kernel.
The getBuild() function defined in /etc/init.d/tc-functions is used to determine whether you need 32 or 64 bit extensions:
tc@E310:~$ . /etc/init.d/tc-functions && getBuild
x86
tc@E310:~$