I would suggest taking into account the following:

(1) Nominalization historically used 'that' (building a noun out of a
phrase with a verb was done with such phrases which had 'that' at the
beginning)

(2) Wh- elements were seen mostly as tending to indicate potential more
than actual truth values.

(3) When 'who' is used to nominalize it's usually in "whoever" or "he
who..", which supports points (1) and (2).

That's, in short, the news from sunny Israel.

Shalom,

Ioram Melcer