The phrase "illustrative purposes" means something is being used to show or demonstrate an idea, without being used for its original or normal purpose. Full definition
The example is hypothetical and provided for illustrative purposes only. (schwabcharitable.org)
This MTA index forecast has been prepared by Mortgage - X for general illustrative purposes only. (mortgage-x.com)
Some who shall remain nameless, but for illustrative purposes lets call them David Starkey, saw the fires of discontent and thought it wise to pour petrol on them by invoking racial stereotypes. (theguardian.com)