Perhaps better to try to illustrate. The | is my cursor.

First I write somethinge.

First I write somethinge. |

Find a typo, so backspace thrice, previous space disappears

First I writesomething|

Insert cursor, try to add space, accidentally add an N due to small onscreen keyboard.

First I writen|something.

Backspace to remove N, word contracts again.

First Iwrite|something.

It keeps going until the entire text field is one gigalarge single word.