Paul's purpose in reassuring these, changes nothing about what the verse says.
Nope your attaching the buzz words beginning to mean ' BEFORE the foundation of the world ' .and CHOSEN to mean the same thing . But the verse says BEGINNING and chosen you to salvation THROUGH !!!! ( the vehicle ) sanctification of the Spirit and belief of the truth: As opposed to Enduring the wrath of God and missing the return of Christ. Just the same as God has chosen all those in the Church age the way of salvation is through sanctification and Believing the truth . From the beginning this has been the plan . From the beginning when Paul first shared the Gospel with them ,this has been the way . " So don't fear ,you are on course " . 2 thes 2.5
The context. Just a few verses before ( always read the context.
1¶Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,
2That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
3Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
4Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
5¶Remember ye not, that, when I was yet with you, I told you these things?