The trust level required with Signal is, "do I trust the people in this chat not to share the specific communications I am sending to them with some other party whom I do not want to have a copy".
There are many many situations where this level of trust applies that "trust" in the general sense does not apply. It is a useful property.
And if you don't have that level of trust, don't put it in writing.
TM SGNL changes the trust required to, "do I also trust this 3rd party not to share the contents of any of my communications, possibly inadvertently due to poor security practices".
This is a categorical and demonstrably material difference in security model. I do not understand why so many are claiming it is not.