It starts the loan over which is why the payments drop “reamortize” yes you have to request it, they aren’t going to deny it, they want your money. It is not a wash, you save on the interest and you can keep making the same payment if you want or save the difference to make another recast payment down the
line. They will send you a whole break down of your new monthly payments,interest included and unlike refinancing, there is NO closing costs or costs period
Look up recast calculator and put the numbers in
You aren't wrong, I can see the additional flexibility with a recast, so I am glad I learned about it.
It's a wash if you pay the new lower monthly payment, the total balance, interest on that balance, and money saved on interest will be the same.
However, if you could make the lump sum payment and afford to pay extra on the principle the same amount the recast would lower your payment by, then you would save just as much in interest, but it would be paid off faster.