Error about @disabled constructor when there is a custom one

[Minas Mina]

 From Jonathan M Davis:

"...At this point, I don't think that the situation with default 
constructors and
structs is going to change. It's a result of requiring init 
properties for all
types, and is thus a "forced fault" in the language..."

Why does requiring init properties for all types results in this? 
What does that even mean?