Question was asked about why Yud Bet Mem, the 70th of the names of God has a regular Mem and not a final Mem.

-----Keep in mind these 72 names are generated by using the Atbash cypher.

Exodus 14: Verses 19-21 are the source for these names.
There are 72 letters in verse 19 and verse 20 and verse 21.

Take the 1st letter of verse 19, which is Vav, Take the last letter of verse 20, which is Heh.
Take the 1st letter of verse 21, which is Vav.
This generates the first name, Vav Heh Vav.

Take the 2nd letter of verse 19, which is Yud, Take the 2nd to last letter of verse 20, which is Lamed.
Take the 2nd letter of verse 21, which is Yud.
This generates the second name, Yud Lamed Yud.

the direction is right to left starting from the first letter with verse 19
left to right starting with the last letter of verse 20
right to left starting with the 1st letter of verse 21

Verse 19 contributes the first letter of each name
Verse 20 contributes the 2nd letter of each name
Verse 21 contributes the 3rd letter of each name

Follow this sequence until you reach Yud Bet Mem
This is the third to the last name or the 70th name.

Yud Bet Mem is generated by taking the 70th or third to the last letter of Exodus 14 verse 19 which is Yud
The third letter of verse 20 which is Bet
The 70th letter of verse 21 which is Mem (not final)

It is a code, a cypher.