Please elaborate

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. That he was late, did not seem to bother him.
  2. Though he was late he didn’t seem to bother him.
    Is #1 correct grammatically?
    Does #1 mean #2?
    Please elaborate. Thanks.
2

2 is incorrect grammatically.
1 is not an ideal way of stating this.

It did not seem to bother him that he was late
is the natural sentence.
2. should be
Though he was late, it/this didn’t seem to bother him.