That's strange, although renovateur is a cleaner and conditioner itself, I doubt it possesses any property or feature to strip the leather's colour, unlike renomat. The neutral formula will not change the color of the leather but it will moisturise a pair of shoes whose natural patina one does not want to change. It will rather provide deep, essential nourishment to your shoes.
Maybe, that lad you mentioned, applied way too much renovateur on his new shoes to cause the shade to be matte-like. Renovatuer should be used sparingly and not subjected to scheduled timeframes. This is subjective. Ultimately, the onus is on the wearer to inspect and decide when's the need for renovateur application.
Personally, I will wear the shoes few times before applying any renovateur/cream/wax. The pores have yet to fully open and ‘accept’ the polish. The older the shoe, the easier to polish. But that's just me.
If it was used on custom patina shoes, there is a high chance that there will be some colour run. Otherwise it shouldn't be too drastic. I'm curious to what extent was the colour stripped to. I wonder what shoe it was... I've even tried using renovateur on Pedro and Rad Russel shoes, no problem at all.

