Inaccuracy in the lesson for beginner "Don't Forget Your King"

In the lesson Don't Forget Your King at position

you are asked to "Count the material - who is ahead? Now look for hanging pieces - can you take anything for free? Now look at your king - is it safe yet? After you've thought about all three of these things, decide on the best move." But after Rf8 I've got the message

and task after O-O was done with score 70%.

The analysis of this position show that Rf8 is better move then O-O:

This two moves are actually equivalent, so I think Rf8 and O-O must be both correct answer with score 100% and message for one of it:

And this is after 30 minutes of computer analysis, right? Or are we talking closer to 30 seconds, which would completely invalidate your claim!

Analysis takes about 30 seconds. How it affects on the "incorrect" Rf8?

I think that move Rf8 is even more correct than O-O. The analysis confirm my opinion. This is why I post the analysis.

30 seconds of analysis is not enough to correctly evaluate the position.