Amplifying it would be pasting images and links to Parler all over the Google Play splash page and all over the Google Play website, sending emails to all its gmail users to download Parler, or inserting Parler ads into some % of its ad impressions.
They aren't doing that. "Leave it alone" is not the same thing as amplification, that's literally the distinction that is made in Section 230.
The ONLY thing being asked for is that Parler polices itself (or the authorities get involved where appropriate), and that Google and Apple leave it be because all they do is serve as the conduit to get it onto the device they control.
That is the way the world SHOULD work. No it doesn't give you the adrenaline rush of enforcing your desires on the world, but that's not a good thing to be enabling in the first place.
If they had no control over the stores used to get apps on devices, the whole question would be moot. Their duopoly leads to this issue. Frankly, that control should be taken away.