Question on upgrading data retention

As I contemplate taking the upgrade offer, to upgrade from 8.1 to 10, I have been doing some reading here in regards to the upgrade process. Since I am not changing out motherboard, I would prefer to try the upgrade first rather than the pain of a clean install.

Anyway, I have 4 physical drives, one of which has three partitions. Two SSD's ( One has Windows and programs, the other games), and two hard disks that have data on them.

I guess my thinking is, by doing the upgrade route, it will preserve everything that I have installed for Windows 10, like all my games along with their settings.
Now in reading the Windows 10 Upgrade installation tutorial thread in the forum, is states:

2. Temporarily disconnect all non OS hard drives until Windows installation has finished. This is to avoid Windows Setup from installing files on other hard drives by mistake.

So I was thinking I could just leave everything connected as is, and the upgrade would retain the appropriate drives and data on them. By disconnecting, how is it going to do that?
Or is this referring more to doing a clean install? I know whenever I do a new system build, or replace the motherboard, that is what I do, just have the C drive connected.

Thanks for any tips, just trying to wrap my head around everything in preparation for when I do the upgrade.

BunnyJ said:

From my experience I never have unconnected my secondary drive(HDD) when I update the OS on my primary(SSD) and I've never encountered any issues with the drive and the data on it. When done the data and drives are there and the letters that were assigned are the same.

Just my experience,,

That is kind of what I was thinking as well. Certainly I will have full recent backups of all my data stored on an external hard drive, just in case something should happen with the data on any of those drives. But I was thinking it should retain the drives along with the drive letters and data on them.

Thanks,