Wording in K&R Strcpy code about pointers being passed by value

On page 105, the authors provide the following example:

The authors state:

Because arguments are passed by value, Strcpy can use the parameters s and t in any way it pleases.

Should there not be a caveat here that this freedom only applies to s and not t? For instance,

would be disastrous at the caller site.

That is, even though t within strcpy is a copy of whatever pointer is the actual argument (say T) at the calling site, i.e., aren't the following asserts valid

Godbolt link of above : https://godbolt.org/z/Ycfxfess6

So, there extends to s some freedoms (for e.g., one can arbitrarily write into it garbage before doing the true copy) which t does not enjoy.