I get what you are saying. Basically the sudo binaries were like superuser/supersu binaries (maybe an overly simplistic comparison). And the apks just make it so you have to approve an apps permission to use said binaries. That would be why I needed to flash something in recovery or use gingerbreak to get the superuser binaries to use the superuser apk?
Nope.....
It has nothing to do with running gingerbreak or flashing from recovery .basically apps acquire rooted shell perms. from su binary .
The whole purpose of rooting is to push su binary to /system/xbin or /system/bin . Method doesn't matter .
Method one :Via Custom recovery .
Which you did ....
Method two :via manual broken shell .
You can use broken shell(its pretty simple just a line edit in init.rc) .Then you can manually push the binary in the phone and set permissions and all and get root running .
method 3 :via broken shell(automatic)
The HTC One X root method .If you have gone all the lengths to break shell ,you may as well use a one shot method to install su binary at first boot .
methods 1,2,3 require unlocked bootloaders and/or odin and all since you are either flashing recovery.img or boot.img or so ....
Method 4 : Lets Break Android
This is special method . By this method you break a live system .
You see ,rageagainstthecage(ratc),psneuter ,Gingerbreak ,zergrush are all exploits .
When you run these on an android powered device ,a relevant device system breaks and a temporary access to rooted shell(#) is created . Using this temp access ,the su binary is pushed in /system and your phone is rooted .Some exploits are android wide ,some are phone wide .
The exploit is active till a reboot .Thats why it is advisable to reboot phone after rooting with such method .
Google doesnt care about the first three methods .They are technically harmless and the end-user is responsible for whatever that happens o the phone .
But Google is wary of this last method since all of them are
security exploits . Because all the notorious malware use this exploits
Droid Dream used ratc
Fake Angry birds use Gingerbreak.
Now if an app had used your sudo binary to push it's modified su to control the device then it would compromise .Hypothetical but not impossible
.
My guess is sudo doesn't give write permission on /system or wherever the su binaries need to be
Edit: you could test with an unrooted phone and root explorer file manager...
who needs write permission !! if it breaks the shell ,you just need a busybox to acquire a write permission .