Carbon sequestration deployment check seems to be too big: it requires consuming 1.5b CO2 and producing 2b O2. I am now waiting for it to proceed with bio-research (botany 1) but I've only consumed 1.2b O2 (254m of comp. and 173m uncomp) and produced 1.63m O2 (351m comp and 231m uncomp). I am only 80% through this check.
Looks like my decision of avoding venting has backfired and I need to run my factory afk just to get this completed.

Shouldn't this check be lower?

Part of the end game is increasing oxygen levels in the atmosphere. By the time you reach this checkpoint, you have 2 new options for mass producing oxygen, one of which also consumes CO2. This seems like a good point at which to make a little plant that converts CO2 into O2. With the extra carbon you get you can either try to warehouse it for making coal or use the solid waste recipes to dump it.

Carbon dioxide electrolysis in a tier 3 electrolyzer consumes 400 compressed co2 per second (equivalent to 1600 regular co2 for the purposes of this requirement). 10 of those would be approximately 1 million co2 per minute. The next step (carbon deposition) will recycle some co back into co2 to go back through this process, which is fine, since production doesn't counteract any progress toward consumption.

This process will fulfill your co2 needs quicker than your o2 needs. So you can supplement with the other new method of oxygen production, algae farming. Algae converts air into massive amounts of oxygen, which you can vent to make progress toward your oxygen mission goal in the long term as well as this checkpoint in the short term.

The overall atmospheric oxygen goal will be a lot easier if you set it up earlier and have these oxygen plants churning away in the background, rather than leaving it to last and having to wait.

Thanks for the hints. I have not considered that a checkpoint might be designed to steer towards the end game goal.
I find it a bit weird that a checkpoint that you always use to slow down the progression (congrats on wube adopting your idea, btw!) is used as a kind of enforcement to build a part of the factory that is not really useful for tech progression.
My plan with the oxygen goal was to use algae for the oxygen goal (I've done 40% already and I was checking what the effect of this was on oxygen goal). I really enjoy the end game shift towards biology and I somehow expected this part of the gameplay to be a part where I achieve the end game goals. I also find that artificially consuming CO2 only for the sake of achieving an arbitrary target does not make a lot of sense in the scope of what I know about the mod so far.
In short, for me this is the only checkpoint so far, I would gladly see removed or changed i.e. to 30% oxygen goal.

Another idea here might be to add a goal of removing a certain amount of CO2 from the atmosphere. The use of industrial machinery to capture and convert it to carbon as it can be done now (releasing a lot of oxygen in the process as a nice side effect). It would in my opinion be a bit clearer to have a goal formulated like this.

The way that oxygen is counted, you get diminishing returns from a single source, so you are encouraged to a variety of methods rather than going all in on one. You'll want at least a little oxygen venting. Some people get it from their normal factory operation, but some people are also way past that checkpoint by the time they get to it.

There is a carbon sequestration goal in the form of coal and petroleum mission objectives. That's what they do. Oxygen venting is consistent with that since it gives you a lot of material you'll need for that.