Even more trouble from a closer reading of SRFI 14:

char-set:blank          space and tab
char-set:graphic        letter + digit + punctuation + symbol
char-set:printing       graphic + whitespace
char-set:whitespace     space, newline, tab, FF, VT, CR

So the "printing" characters include ALL whitespace characters, not just
the space character.

That means it would be misleading to use "ascii-printing?" to refer only
to the space character + graphic characters in SRFI 175.

I still believe an "only space + graphic" procedure is more
useful/reliable than an "all whitespace + graphic" procedure. The C/Unix
world would seem to agree. Common Lisp does too. ANSI CL does not define
a tab character but CLISP, SBCL and CCL all say (graphic-char-p #\tab)
is false.