There's nothing misleading about the statement that the Holy Spirit guides Ecuмenical Councils. This does not mean every sentence is infallible, but you're fixated on infallibility. What it does mean is that it prevents an Ecuмenical Council from being a garbage bin of bad doctrine.
Again, this is a generalization without outlining the specifics, which leads to a faulty conclusion.
1. Can there be an ecuмenical council without the pope? No.
2. Can anyone besides a pope be infallible? No.
3. Can an ecuмenical council be infallible without the pope? No.
Conclusion - For a council to be ecuмenical, the pope has to be involved and approve it.
4. How does the Holy Ghost guide the church? By the pope's infallibility and Apostolic truths from Tradition and Scripture.
5. Is there any other way that the Holy Ghost can guide the Church? No, this is the only power the pope has for teaching.
6. Apart from Infaillibility, is there any other way for the pope to be protected from error? No.
Conclusion - A council cannot be infallible unless the pope uses infallibility.
7. Does a pope need an ecuмenical council to proclaim an infallible teaching? No, he can teach authoritatively apart from a council.
8. Can an ecuмenical council proclaim an infallible teaching without the pope? No, only the pope is infallible.
9. If all the bishops of the world agree on something, but the pope does not teach authoritatively, is such a thing infallible? Depends. Yes, if such a thing can be proven to be part of Scripture/Tradition (i.e. it has always been true).
Conclusion - Something is infallible if a) the pope teaches authoritatively or b) a non-authoritative truth is proven to be "always held" from Tradition/Scripture.
10. How does the Church teach authoritatively and error-free? The pope uses infallibility, either solemn or ordinary/universal.
11. What is ordinary/universal teaching? When the Church (bishops, cardinals, etc) reiterates a teaching from the past, which has been shown to be of Tradition/Scripture.
12. Outside of solemn/infallible teachings and Tradition/Scripture, is the Church protected from error? No because only these tools are from Christ.
Conclusion - If the Church does not teach using infallibility or Tradition/Scripture, then She isn't teaching authoritatively, thus She can err.
13. Can an ecuмenical council, without the pope engaging infallibility, be guided by the Holy Ghost? No.
14. Can an ecuмenical council, without the pope engaging infallibility, err? Yes.
15. Does indefectibility protect the Church from error? Indefectibility is an attribute, not a power. Infallibility is the power/means the pope uses to keep teachings indefectible.
Conclusion - The pope can err if he speaks non-authoritatively and on non-Tradition/Scripture ideas because such aren't protected by the Holy Ghost.
16. If the pope speaks non-authoritatively, is this part of Church teaching, doctrine, law? No.
17. If the pope speaks on matters non-Traditional or non-Scriptural, is this part of Church teaching, doctrine, law? No.
18. If the pope errs, because he does not teach authoritatively nor infallibly, does this affect the Church's indefectibility? No.
19. Do papal non-authoritative comments, homilies, writings, change Church doctrine? No.
Conclusion A - If the pope errs, this does not affect perennial Church doctrine, nor does it stain the purity of Church Teachings.
Conclusion B - A pope's error has no authority, therefore it is not official teaching, therefore it does not affect or negate the Church's indefectible nature.
20. Did the pope teach authoritatively and infallibly at V2? No.
21. Did the pope use V2 to re-teach previous defined doctrine or did he prove V2 is infallibly based on Tradition/Scripture? No.
22. Is V2 binding under pain of sin and taught as a necessity to be saved? No.
Conclusion A - V2 isn't official church teaching, therefore the pope can err, because he isn't protected by the Holy Ghost.
Conclusion B - Non-official, non-binding, non-salvific councils aren't required to be followed. They are purely optional and speculative theology.
Conclusion C - V2 is speculative theology and isn't protected from error, therefore the Church's indefectibility is not tarnished.