The tribulation is not a test.
It’s a last call come to Jesus moment ... or else.
Your post brought a smile of ‘yup, that’s speakin’ the Gospel in the shortest sentence’. Would you have the verses rewritten? ‘Faith cometh by hearing, and hearing by The Word of God’ to read ‘Faith cometh by fear, and fear by the wrath of God’ ... there will be a vast number saved during the Trib, but it will be from fear, unlike the Saving faith during the Church Age. What Jesus said to Thomas following the resurrection comes to mind at the end of this Age.
Or are they just going to be believers with no understanding? Maybe they can just read all the popular Christian books that get left behind.