Indeed, I thought that for such a connection, MCT would be 105 minutes or thereabout?

If this is two separate tickets (ie not a connection but rather a self-transfer) then it is a very unsafe one. Transfer busses from T4 to T5 can be quite sparse depending on the time of day (I didn't check flight times) and the transfer itself takes a little while, plus passport control here so even with a perfectly on time arrival, making conformance at T5 is far from guaranteed, let alone with a delay.