Are you sure it's "teases?"
Something more extreme seems more fitting

This translation surely looks fishy.

Well you can check out the raw at post #35754

Saber:
"Caster, I feel the same way"
"Let's make a challenge so the most caring mother wins! "
(something like that)

Caster
"Uhuhu, that's what i wish for, Saber-san."

Rin
" Uwa... The rules were changed into something strange..."
"Rider, are you okay with that too?"

Rider
" Master is a cruel man. Everyday, everyday, he abuses me so badly. When i realized, my belly... "
" Guess i can say i don't care anymore with the Holy Grail."
" This child in my belly... and me too... I wish all of that disappear."
" (I) would rather (prefer) you kill me."

Sakura
" Oneechan, the darkness made me pregnant... "

Kirei
" Isn't giving birth a blessing?"

Rin
" Kotomine, this time I give up."

So, Rider got pregnant by Shinji?

Damn, poor Rider. They use that as a punishment for murder in some courtrooms.