They did this possibly for several reasons, persons that put ALL firearms and suppressors in their trusts will unknowingly submit this to be able to register their braced pistols for the exemption, not knowing that it will pretty much be a full list inventory of what they actually posses. That and ATF wants to limit the possession to one sole person to where once the possessor is no longer able to have said firearm(s) it cannot be transferred to any others, if filed individually.
Not sure I follow you, even if I file as an individual I can still transfer it on a form 4 to another or to my heir on a form 5.
Anywho, their documents state that the items need to be added to a trust prior to the date the rule is published in the register. Their going to get some heavy pushback on that 13th date.

