Question: lprint(%) not working

Just for my interest.
Why is the following not working

one := ``(1);
                           one := (1)

 lprint(`%`);
Error, Got internal error in Typesetting:-Parse:-Preprocess : "invalid subscript selector"
Typesetting:-mambiguous(Typesetting:-mambiguous( lprint(%), 

  Typesetting:-merror("Got internal error in Typesetting:-Parse:\

  -Preprocess : "invalid subscript selector"")))

but this works

lprint(one);
``(1)
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