I've used phantom centre for years with horn/CD based speakers and direct radiators (KEF 104/2). For a brief time I used a KEF coax centre with the 104/2, but found the difference trivial.
Re DD signal compression with no centre: I've read this is so, but seen no actual evidence so far beyond assertion that this is the case.
As I don't use the internal amplifiers it's moot for me anyway, as I simply mix the C into L&R at line level post AVR.
“You are not special. You are not a beautiful and unique snowflake.” Chuck Palahniuk