Don't worry, franky1 gave a bit more detail in case my wording could be considered as misleading.
There is no "reserved for future use". Franky is a misleading statement incarnate.
The Segwit testnet mined a 4MB block, just by including alot of multi-signature transactions (which obviously have a much heavier transaction:signature ratio than regular transactions)
Do you have any arguments that don't involve subverting plainly observable facts?