The subject was diffusers before 'we' gave you-know-who the boot.
The T33 is a T50 without the active diffuser. There is no fan to pull air up into the roof of the diffuser, but ramping up from the midpoint instead of the rear axle line moves the effective point of the downforce forward.
Then there is [apparently] a diffuser ahead of each front wheel that together provide 30% of the total downforce.