I have been following the exact steps as outlined in this tutorial video, with no oddities happening along the way: https://youtu.be/twQbHWJF7LA
Well, I was able to follow it up and until we got to the Partitioning part, where he says to load DOS up in the machine, presumably meaning the PC-10 in this case.
The PC-10 loads the ISA IDE to SD Adapter just fine, it even tried to look for Drive C (The SD Card) for like 10-15 seconds, until giving up then and there (as seen in the pic).
(ISA IDE to SD card Adapter i got:) 
In other words it seems that the Adapter either doesn't recognise what is on the Card and I've done something wrong in burning the provided image onto it or formating, or it doesn't recognise the card itself to begin with. Its a Brand new 32GB SanDisk SD so that be pretty suprising...
In other words... im out of ideas... i tried different DIP switch configurations and all, but no change. Perhaps the PC-10 III Simply doesnt like the Adapter... or can't run 6.22... im just out of ideas and frustrated. I've had this thing for over a month now with no luck in seeing it run once properly, and original 5,25" DOS Bootdisks are expensive and take a while to arrive. Should I just bite the bullet and go for one? I don't know. Any advice is much appreciated...
Just some thoughts off the top of my head.
I did try to see if leaving the partitioning part out changes anything, and still nothing. Same thing as before. Also tried not changing sizes, same thing sadly.
As for the other 2 points, im afraid that I don't have the knowhow yet as to how to check those...
I'm not familiar with the tool they talked about for burning the image to the SD card, but can you share a screen shot of the options you used when burning the image?
I'll do once im home in around 7 hours! In the mean time, I can definetly say that what the Video shows is 1 to 1 the same thing I saw while working with both programs and I followed them to the Pixel if that helps
Just got around to taking some screenshots.
First I press the "Flash from File" button and choose the DOS6.22 Ultimate .img
Then I select the Target, which is the SD Card
Then Lastly I press the Flash button and it does its thing
All ending without error on this screen
This is what the finished thing then looks like
Then I'd usually move onto the Partition Wizard.
Something odd I just noticed is that even after all the flashing and stuff, the card retains its original thumbnail saying "SD HC", would've thought that be gone by now, could that be an issue?
Ah! SDHC.
So, SDHC cards are a little different than regular SD cards (the protocol used to communicate with the card is a little different) and often aren't supported by particular SD card readers like potentially the SD-to-IDE adapter you're using.
(I know back in the day, I hacked my Nintendo Wii, which involved loading a bunch of homebrew programs on an SD card, and at first it didn't support SDHC cards until there was a firmware update.)
Technically, I think any SD card can be SDHC, but almost always SDHC is only used by high-capacity cards. Also, I think they usually say "SDHC" physically on the card.
So, probably the next thing I'd try if I was you was to change out your SDHC card for a non-HC SD card. Any 8GB to 32GB card should be fine, I'd think. (If you have any that are smaller even than that, like 256MB, even, you could at least use it to confirm that's the issue. You just couldn't expand the partition sizes out to 2GB.)
I see, in that case I'll go to the store tomorrow and see if they got a tiny non HC SD card! Thank you!