filtration and carbonation (in secondary) questions

[perfection]

01. in the conditioning tank does the reduced yeast concentration contribute any carbonation as almost all the fermentable sugars are consumed and the beer is already normally saturated with close to 1 volume of CO2 in the primary - so why are brewery secondary tanks to which 'green' beers are racked for conditioning tank pressurized or airlocked? Is this pressurization needed only when priming sugars or krausening or force carbonation is carried out and NOT otherwise? If (force) carbonation is to be done after filtration there is no need to pressurize the secondary tank?

02. Can the beer be centrifuged and (rough and/or sterile) filtered after being carbonated and does it not release the CO2 or are such processes conducted under pressure too?

Thanks