Is there a difference?

It doesn’t have to be100% exactly what they said, but yes that is the idea, that it is reported speech you can think of と as “” marks.

Such as something like “My friend told me they’d go at 11” 11時に行くと言う even though they may not have literally said those exact words. Versus “My friend told me their plans” 計画を言う

Excellent, thanks a lot!