That's an incredibly limiting position to take, especially with regards to Power Rangers. By taking that position, you discount a number of things that are part of the fabric of the PRU's overall tapestry.
Do you have some examples? But please don't say Scorpion Rain.
Billy (Blue MMPR Ranger) and Jen (Pink Time Force Ranger)'s last names. They are officially recognized as being Cranston and Scott, respectively, but they were never said in-show and were provided instead by officially recognized auxillary materials.
There are also other things that are recognized as being official parts of PR lore but were established out-of-show, but those are the two examples I could think of.