Exchanges do not replace a mixer or a proper coinjoining service. You can sue it it you're trying to blur the transaction trail at a basic from family and friends but your transactions are logged by the exchange and they are liable to share that information and can lose it through a breach.
Meaning if i do multiple transactions using that Instant Exchange and convert Bitcoin to Litecoin. (The destination address of LTC remains the same in all the transactions )
AFAIK exchanges use multiple addresses and you will not get the same one each time except at the point of deposit (which they change sparingly for each user).