It does make a difference.
If there are two checks and you have TEN=150% while attacker has POT=100%, then with a two check process you would have:
First check: 50% chance to resist
Second check (if you fail to resist on the first check) = 15% chance to resist.
The 15% only applies to the 50% of attempts that didn't resist the first time, so reduce that 50% by (0.5*0.15) and you get 50% - 7.5% = 42.5%.
Two checks changes the odds. Two checks is not correct. There is one check with a minimum chance to resist.