My point was that it would be better to achieve that with one of our own players, developed and improved by Bielsa, than by developing and improving an Arsenal player we've no chance of signing permanently.
Your question was "what’s the point of Bielsa improving him even more just to hand him back to Arsenal?"
I just answered your question.

Of course it would be better to do it with our own players but the loan players are usually not affordable and/or available to buy, hence the loan.

only the ‘I know better than Bielsa brigade’ thought wtf 
