Body shapes are a complete mess. Why do their head sizes keep changing? They have like shrunken heads.
Massive arm in one panel and thin arm in the third panel??? https://dynasty-scans.com/chapters/itoshi_koishi_ch01#10
Jin Takemiya has her own style. It’s artistic and not meant to be exactly proportional. If everything is supposed to be proportional, it’s boring. She shoots more for expression than proportion.
Heck, even people who do draw proportionately make mistakes. Artists are not robots.
It's not only the fact that it's not proportional that's the problem here. It's the inconsistency. Their body shape keeps changing from panel to panel.
In some, they can be described as feminin (tho with the now recognisable Jin breasts) and in other they are giant (or their head must have been magically shrunk) with the shoulders of professional rugbymen.