What you can not do is send from an exchange where you dont have the private key, such as Bittrex.
This is not because there is anything wrong with Bittrex, it is just because Bittrex and other altcoin exchanges like it are not designed to be used as an online wallet.
You need to know the differerence between an online wallet and an altcoin exchange.
I think that you are confusing things....
That is a problem when you are buying a ETH tokens, because they send the tokens back to the address that you used and you don't own this address.
In this case we are talking about a COIN, and they will be hold at my.electroneum.com until you can transfer them to a Pager wallet or desktop wallet.
Basically, it is FINE to fund your account from an exchange.
Cheers
MC