wconsteriods does not accept input from standard in, wc does.

[pacmaninbw]

[tms13]

POSIX wc spec says:

The standard input shall be used if no file operands are specified, and shall be used if a file operand is '-' and the implementation treats the '-' as meaning standard input.

and:

If no input file operands are specified, no name shall be written and no characters preceding the pathname shall be written.