I also created a "Watching only wallet" in electrum and put the address in it.  Of course Electrum shows the bitcoin on the address.  I realize this is nothing earth shaking.  But wondered if I did derive the private key from the seed if I could "add" that to the watching only wallet to enable me to send the bitcoin out of it?  I might experiment with a small amount of bitcoin of my own.  Create a wallet.  Move a small amount of bitcoin to it.  Then open a watching only wallet.  Create a private key from the mnemonic that I got from the first wallet and see if I could send coin out of my watching only wallet with that key?  I'll let you know how the experiment goes.