What determines 6x9 speaker fit

I have a 2014 tacoma double cab. I have an opportunity to add some jl audio c2 690 TX 3way 6x9s to the front doors but Crutchfield and other audio sites say they don't fit as apposed to other jl audio 6x9s that do. I'm aware of adaptors etc... but is it a magnet depth issue or speaker grill on the door interference issue?

 

They seem to think that there is less depth than there actually is. I have used several pairs that they say don’t fit.

with that being said, I wouldn’t do 3-ways unless you get them stupid cheap and just want them

 

If I may ask, why don't you recommend the 3-way 6x9"s? I have some and love the way they sound

 

I'd like to know as well