This is 3 lines of text in a complex scene in WaL:
Python:
show abusmall ewide sangry
show pov enarrow hfneu2 hbneu2 msmile bangry scrazyhair
show rose basemessy xwings xhornsnude enarrow bangryn msmile at s_left:
xalign -0.5 alpha 1
$ renpy.music.set_volume(0.8, channel='sfx4')
play sfx4 "audio/magicdemon2.ogg" fadein 0.5
abu "WHHHHHAAAAAAATTTTTTT?!" with vpunch
show rose eneu bupn
show pov hfreach eclosed bup at m_left with moveinleft:
xalign 0.3 xzoom -1.0
show pov hfneu2 eneudown
show abusmall at t_right with moveoutleft:
xalign 1.5 xzoom -1.0
show pov hfneu1 hbneu1 bsad mneu
show abusmall at t_right with quickdissolve:
xzoom 1.0 xalign 1.5
show rose bsadn
show abusmall eangry sangry
with quickdissolve
pov "Ah, Rose, I was worried you wouldn't come."
show rose ewide bupn mneu
show pov ewideb bup mcry
show abusmall eangry
abu "WHAT HAVE YOU DONE?!" with vpunch
And that's basically the same for every piece of dialog. That's what they call 'posing'. This coding structure you see above needs to be done for every single dialog line in the game (maybe on a different scale, but still), and then you need to replay the scene taking extra care to detect if every single one of those short orders works as intended and make actual sense. Of course, if you edit the dialog lines, all those orders need to be adjusted too, and then checked once again.
Creating a minigame or a turn-based combat system surely takes longer than 'posing' this scene, but it's usually a one-time thing and then all you'd need to do is add a 'call screen' line and maybe adjust the variables involved before that 'call' statement. There, a bug can only exist within the minigame's core, and it would be easily detected as it would crash the game altogether or make the minigame not produce the expected result (it may take several days to fix, sure, but again it would be a one-time thing and you'll then have your minigame's code all fine and dandy for every time you'd want to use it in-game again). Taking care of different variables and paths is complex too, but that's just a matter of carefully noting down every possible combination and not messing with the variables' names; again, bugs would be easily detected and way easier to fix than those in minigames. Having a myriad of those variables and paths is probably similar to what posing means for WaL in terms of complexity, except you only check those variables every once in a while, after a significant interaction, while posing is needed for every single dialog line.