About omitting ということ in relative sentences


I was reviewing some concepts about the use of ということ in relative sentences,
and there's something I still can't quite understand.

Looking at the sentence:

> パンジーが食べられる花だということは知っている (I know that pansies are edible flowers.)

Is the ということ here necessary? Since the first clause ends in the noun 花,
doesn't something like this has similar meaning?

> パンジーが食べられる花は知っている




> パンジーが食べられる花だということは知っている

This more literally means: "I know **the thing that** pansies are flowers whom
(somebody) can eat.".

こと ("the thing") is direct object of 知っている, and という can be translated as
"that".

> パンジーが食べられる花は知っている

After dropping of だということ, 花 becomes direct object of 知っている, so this sentence
could mean e.g.:

"I know flowers whom pansies can eat."

"Pansies know flowers who are eaten."

"Pansies know flowers who can eat."

