Not heard of this before, but IIRC, the ‘pull’ from a HH account only works for a flight booking. Not even the reverse, so when you get a flight credit it only goes to your account, the credit is not spread across all of the accounts in the HHA.

Have you done the maths to work out whether (at 1p per Avios) it is still a good deal? And if you need more Avios, would the maths still work in your favour if you bought some more using e.g. Balance Booster?