A high point share for Crosby/Malkin was the exception, not the norm. They notably were able to produce a lot more consistently apart from each other at ES which won them a Cup in '09 and got them to the SCF in '08.
Here is a comparison of how the teams did 5 vs 5 with the pairs.
Crosby and Malkin 2007-2008 and 2008-2009
Crosby and Malkin
TOI 710 GF/60 4.14 GF% 62.82
Crosby without Malkin
TOI 1149 GF/60 2.82 GF% 52.94
Malkin without Crosby
TOI 1683 GF/60 3.1 GF% 56.86
McDavid and Draisaitl since 2022-23 (including a down year last year for Leon)
McDavid and Draisaitl
TOI 1081 GF/60 4.55 GF% 62.60
McDavid without Draisaitl
TOI 1912 GF/60 3.48 GF% 54.4
Draisaitl without McDavid
TOI 1937 GF/60 2.92 GF% 52.81
Over these two periods the pairs played together roughly the same proportion of their minutes and the results separately and apart do not distinguish the two pairs.
Now what is true is that if you were to look at Pittsburgh nearer their second cup run with this pair they did not play all that much together or have much success when they did. From 2015-216 through 2017-2018 they played 58 5 vs 5 minutes together and the team scored 0 goals when they were on the ice.
Crosby without Malkin
TOI 3534 GF/60 2.92 GF% 55.31
Malkin without Cosby
TOI 2728 GF/60 3.08 GF% 54.25
In fact separately the pairs are very similar. The big advantage comes when they are together. But unlike Malkin and Crosby whose styles don't jive all that well, what makes McDavid and Draisaitl work so well is that Draisaitl can play a completely different style of game when paired with McDavid to complement him than he does when he plays alone. This is one of the unappreciated aspects of Draisaitl's game. He reinvented himself precisely to play with McDavid. On his own he is a pass first guy whose instinct is to slow the game down and control possession. With McDavid he becomes a shooter, playing an up tempo give and go game.