So hard, in fact, that I still haven't figured it out.

When I try to set a filter on a true/false column I get the following options:

Has Any Value
Equals
Does Not Equal
Is Blank
Is Not Blank

Which of these actually pertain to a true/false column?
Has Any Value? I get everything.
Equals true/True/TRUE? I get nothing.
Does Not Equal true/True/TRUE? I get everything.
Is Blank? I get nothing.
Is Not Blank? I get everything.

Maybe the choices should be simply:

Is True
Is False

Sure would be clearer to me. Can you give me a workaround trick that allows me to actually differentiate True and False with the current filtering options?

Equals True
Equals False
Does Not Equal True
Does Not Equal False
all work now.

Also, if you try to do something else like:
Equals Yes
then you get the error message "String was not recognized as a valid Boolean".

All of those filter options ("Is Blank", etc) do pertain to a boolean column, since all boolean columns in the Document Grid can theoretically be blank if the parent object (e.g. "Peptide Result") for the row does not exist.