Thanks for the findings but for me i believe these inconsistencies are usually due to the aggregator OrangeFren data refresh speed and the fast-moving nature of crypto prices, rather than intentional manipulation by the exchanges themselves.
Crypto prices have nothing to do with this since I am looking to exchange crypto for crypto,
and I refreshed my browser and used it at different times to confirm rates are not very accurate.
And it's not a small difference to have almost 2 XMR extra in my wallet.
Currently we check for new rates as soon as we fetch the previous batch.
Bare in mind we also interpolate, we can't query every amount, after all. It also wouldn't be a good design for user privacy to send a request for a quote every time a user searches for a pair, because if any of the exchanges we list had their query history compromised it would make it possible to timing-attack our users. Even if they didn't use that particular service.
Maybe you can add information for users that rates can be different than shown on orangefren website,
this should prevent support having to answer similar questions in future.