macOS Mojave - Native Full screen split


I'd like to ask a question about the native split screen feature in BTT / macOS

I know this subject is controversial..! In that not many people seem to like this feature of macOS, and don't advise using it.
Well - I do like it and I want to use it!

So - I heard on MPU recently that BTT can automate the process of opening two apps and making them full screen / split.
So I immediately bought the lifetime package.

however, I can't figure out how to get this to work.
(Note - I also bought Keyboard Maestro and have tried many times to make the split screen thing work with that - no luck)

anyway -

2019 iMac 27"
macOS 10.14.6 Mojave

I want to open two apps from a macro - and then have one on the left, the other on the right - must be using the full screen split - not just fitting into half a screen each.
(I don't want to hear reasons why I shouldn't do this...)

Is there an example workflow somewhere I can look at to get this working? Because right now I can't seem to get my actions to do it.

what I'm doing now:

Launch App
Launch Second App
Show first App
Open Native Mac OS X Split View for Window (Left)
Show second App
Open Native Mac OS X Split View for Window (Right)

and what happens is:

my apps open... the full screen / split doesn't trigger at all.

what am I doing wrong? Or is this just never going to work?