As pointed out, strength/size is only one metric for the job. I assume like in most other disciplines, women have things offer in various fields that we simply do not, and to some extent, cannot yet understand. A boys club that admits girls is still functioning as a boys club, it would take generations to find a new status quo.
As to strength/size requirements, they are to some degree arbitrary. You pick some average target carry weight. And yet, any one individual you may try to save my exceed that limit...look at the morbidly obese..300, 400, 500 lbs? Sometimes it will take two, and sometimes it will take a team.
And there are other measures other than strength. Someone may not take care of themselves in other ways, or may lack other qualities (drugs, alcohol, lack of endurance, mental fitness, intelligence, leadership, ability to react under stress, etc.,etc) all of which can contribute to inability to perform that duty. In the total "effectiveness", I doubt minor changes to accommodate women are something to fight over. Another way to judge is if the male physical test puts them in the top 20% percentile, the women should be similar in comparison to women.
I think knowledge, experience, and attitude, are far more valuable in 99% of well, everything. I wonder what most preventable errors, life loss, etc., are due to (really). I doubt its inability to carry a little more weight.
I know some former female firefighters, they happen to be big, tough girls. I would be worried if they were little twiggy girls...but that's not the case is it?