IE 11 not being installed on target pc. Why ?

Hello everyone.
I am running WSUS 10.6 on a Windows 7 Pro X64 machine.
And I pretty new to very helpful utility.
I have read many of the postings in this forum and have learned quite a bit.
Currently, I'm trying to understand the conditions under which "UpdateInstaller.exe" will install "IE 11" on a target pc.
Here's two examples:
One:
I start off with a virgin Win 7 X64 pc that, by default, has IE version 8 installed on it.
I start "UpdateInstaller.exe" and click on the "OK" button on the bottom of the "IE11" dialog.
And sure enough, when the update has completed, "IE11" has indeed been installed.
Two:
Now I move on to pc number 2.
It starts out as a Windows 7 Pro X64 machine.
Then, I update "IE 8" to "IE 9". (I ran the MS offline\standalone install for "IE 9" on the target pc.
I then start "UpdateInstaller.exe" and click on the "OK" button on the bottom of the "IE11" dialog.
But this time, "IE 11" is not installed on the target pc.
All the other updates are installed but IE 9 remains.
I'm puzzled.
Can I ask for some help and an explanation, as to when IE 11 will and wont get installed from more experienced users ?
Thanks
JustRay in Wisconsin
I am running WSUS 10.6 on a Windows 7 Pro X64 machine.
And I pretty new to very helpful utility.
I have read many of the postings in this forum and have learned quite a bit.
Currently, I'm trying to understand the conditions under which "UpdateInstaller.exe" will install "IE 11" on a target pc.
Here's two examples:
One:
I start off with a virgin Win 7 X64 pc that, by default, has IE version 8 installed on it.
I start "UpdateInstaller.exe" and click on the "OK" button on the bottom of the "IE11" dialog.
And sure enough, when the update has completed, "IE11" has indeed been installed.
Two:
Now I move on to pc number 2.
It starts out as a Windows 7 Pro X64 machine.
Then, I update "IE 8" to "IE 9". (I ran the MS offline\standalone install for "IE 9" on the target pc.
I then start "UpdateInstaller.exe" and click on the "OK" button on the bottom of the "IE11" dialog.
But this time, "IE 11" is not installed on the target pc.
All the other updates are installed but IE 9 remains.
I'm puzzled.
Can I ask for some help and an explanation, as to when IE 11 will and wont get installed from more experienced users ?
Thanks
JustRay in Wisconsin