What do these three words have in common? flour, tern, thirsty

Question

What do these six words have in common?
Backsplash
Birthplace
Matchstick
Heartthrob
Thousandths
Angsts

Answer 1

Remove one letter from each word and they all spell a number.
FLOUR - L = FOUR (4)
TERN - R = TEN (10)
THIRSTY - S = THIRTY (30)

Comments

Another word that can be in this system will be 'tether'.
tether - t = ether
Unscramble ETHER = THREE (3)

Answer 2

If u remove one letter from all three words then u get number names

Answer 3

They all have an 'r'.