That statement of course is FALSE. In Matthew 24:31 Jesus was pointing to the SAME IDEA that Apostle Paul covered about the 1 Thessalonians 4:13-16 verses...
Matt 24:31
31 And He shall send His angels with a great sound of a trumpet, and they shall gather together His elect from the four winds, from one end of heaven to the other.
KJV
1 Thess 4:13-14
13 But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
14 For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with Him.
KJV
What does that gathering by Jesus of the saints "from one end of heaven to the other" mean? That's about the "asleep" saints being resurrected and then gathered FROM HEAVEN by Lord Jesus and He brings with Him FROM HEAVEN when He comes! EASY!
What's that 1 Thess.4:14 "even so them also which sleep in Jesus will God bring with Him"? That's the SAME IDEA Jesus taught in that Matt.24:31 verse about the asleep saints who had already died being gathered by Him, FROM HEAVEN!
Now for those actually CARE about true study in God's Word, if you take a look at what Lord Jesus said in Mark 13:27 with the last phrase about WHERE He gathers the saints from, you will notice it says they are gathered FROM THE EARTH! Did Apostle Paul cover that in 1 Thess.4? YEAH! He did! That is about those of us still alive when Jesus comes, being "caught up" to Him FROM THE EARTH!
This means Apostle Paul in 1 Thessalonians 4 was REPEATING WHAT JESUS TAUGHT IN HIS OLIVET DISCOURSE about His future gathering of His Church!