pratically yes, your wallet.dat has a pool of addresses on creation after many transaction you can "consume" them and start generating new ones that can be not present in an old backup, this is why is raccomended make regular backups.

this way of work of the wallet was designed for privacy but if you don't like it there's another way go in Settings > Option > Wallet and check Enable Coin Control Features after the restart of the wallet client, in the Send tab you can see Coin Control Features and new field Custom change address here you can put your favorite address for the change/rest, don't put the address of someone else for a mistake  

if you click on the Inputs buttons you can see on which addresses are your funds and even reunite on a single address doing a payment to yourself.