No, she doesn't really become flat side when in motion. Her upper torso remains the same while her hips change with each step which is very plausible but not quite a normal walking posture IRL but it still is a tweaked image to resemble movement. Which to be clear, is an appreciated change w the new design
However, the underlying truth is people don't really pay attention to walking animations for side scroller H games. The real focus belongs to H animations as it's the main content. A great example to this would be another H game called "Goons Raid Her"
Janky walk / run animations but overshadowed by the H scenes it has
"bOoBs DoNt LoOk LiKe ThAt"
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Hmm.... Never realized all boobs must be in uniform to each other when it comes to appearance according to you