Unfortunately, there was no choice. When I clicked either of the links for the "offline" one, it immediately asked if I wanted to install it.
You are confusing two different things:
"When I clicked either of the links", means the act of DOWNLOAD so, unless your browser gave you an option to Save or Run already, and you chose Run, "click on either links" would JUST download the Offline installer.
Maybe you wanted to say: "After I downloaded the Offline installer by clicking the links, I STARTED It from my download folder, and this happened" ?
And the choice of location was locked out.
Of course it was, it's meant to use the location you already chosen for the normal installer, and it's correctly prevent you to make the mistake of installing the Offline installer in a different place.
The Offline installer, as clearly explained in the Sticky post where you download it, is not a "replacement" for the normal installer. It's used in ONE and ONLY ONE case: if you suspect you are not getting the latest code from the regular updater due to network update delays. So it will always be installed last, in the same folder of the normal installer.
If you are not in this situation, you don't need the offline installer at all.
Also, your screenshot doesn't show any products, because you clicked on either the MSFS icon or the P3D icon to hide them, that's why it says "Products are Hidden" so, just click again to bring them back.