Yes, it does, though it varies. From the wiki:
Reverting a capture
When a control point is neutral and both teams are
trying to capture it, captures can be reverted. If a team begins, but
does not finish, to capture a neutral point and then is driven off,
when the other team begins to capture that point, they will first have
to "revert" the progress that the first team made before they can
begin to make progress of their own. The revert rate will increase in
speed with more players of the second team standing on the point.
On Attack/Defend maps, points will slowly revert without being affected by the number of players on the point. This is because, in accordance with the definition, the RED team cannot cap the point, whereas BLU is trying to cap the point. In this way, the point cannot be reverted faster even with additional defenders on the point. Example:
A BLU scout quickly rushes towards the cap, and manages to get in
without anyone noticing him (a RED demo catches a glimpse of him, but barely enough). He almost manages to get the cap fully capped, but to
his utter dismay, the same RED Scottish demolitions expert who spied him turns him
into flying chunks of meat.
A RED Pyro, a RED scout, and a RED Heavy, noticing this event, tries
to stand on the point, hoping to revert the changes made by the
fearsome BLU scout. Alas, their efforts are in vain, because the cap
refuses to revert to normal faster, even with more people on the
Whereas, in a 5 CP map, in modes such as KOTH, or even Arena, where a point can be captured by BOTH teams, both RED and BLU, the amount of players on a point can increase the rate of capture as well as the rate of reverting.
A BLU scout, not coincidentally the same one mentioned previously,
eagerly spies the middle capture point, eager to put his team, Builders League United, ahead of the filthy Reliable Excavation Demolition mercenaries.
He manages to make a heroic effort, getting close
to capping the point, but his efforts are in vain as a patriotic
Russian minigun-toting man shreds him to pieces.
At this point, the point is nearly capped. The RED team would not
like to have the BLU spawns even closer to their base; this would only
make it harder for them to make a comeback. A lone RED spy jumps on
the cap, hoping it'll revert.
To his surprise, it does! It seems to move along slightly faster,
though not as fast. Signalling for help, the RED spy's prayers
are answered as a RED pyro comes in to spycheck. Coincidentally, the
revert rate is now 2X, almost double the efforts of a single spy.
His teammates have all respawned by now, and they all jump on the point. Unfortunately, the point has a max revert limit, darn. But the point is rapidly reverting, allowing them to safely guard the point and revert it to a possession of theirs........for now.
TL;DR my fanfic:
On Attack/Defend maps, where only one team can capture points, points cannot be reverted faster by defenders. However, on Standard Control Point maps where both teams are vying to capture points, points can be reverted faster as more defenders stand on the point, up to a cap of 4x on most maps (more information regarding control point timing here).