"Execute store success" will not update failed commands of an extra subcommand if it is followed by another subcommand, it will however update if it succeeds.

How to Confirm:

Set up scoreboard using the following commands.

/scoreboard objectives add Result dummy
/scoreboard objectives add Variable dummy
/scoreboard players set X Variable 5
/scoreboard objectives setdisplay sidebar Result

Test without subcommands and see that the 'Result' score will be accurately updated.

/execute store success score a Result run execute if score X Variable matches 5

The chat will say "Test passed" and 'Result' for 'a' will be 1.

/execute store success score b Result run execute if score X Variable matches 6

The chat will say "Test failed" and 'Result' for 'b' will be 0.

/execute store success score c Result run execute if score X Variable matches 5 run say Test failed 

The tester will say "Test failed" and 'Result' for 'c' will be 1.

/execute store success score d Result run execute if score X Variable matches 6 run say hi  

Nothing will appear in chat and player 'd' will not be created.