Unfortunately that means that SENs (whose miles are not expiring) would not be able to use expiring miles of (non-status) family members for a companion award.

However it did work "nearly" as expected, at least back in February: For our companion award requiring 52k + 26k, pooling used the 52k from the non-SEN member (nearly draining that acct) and 26 of the booking SEN. I suspect that we would be in bad luck if the non-SEN had less than 26k - in that case I suspect that those miles would still be due to expiry and all miles would be taken from the SEN.