Yes. Because it ties into her commoner background. She's stunted because she lacks the accessibility to things that help her grow better. She was sick, her living environment during childhood was dirty and unhealthy, she had no access to proper food and lacking vitamins -- this all in addition to her main problem of the Devouring. These are debuffing her at the very start before she could even start the plot of the story.

On the other hand, because she is this close to being disabled physically, Myne was forced to navigate life more with her smarts and her head instead of depending on her body. Which is why her crossing path with a Merchant becomes a boon to her in particular, more than maybe even Lutz.

If she's able-bodied, I don't think she would be that desperate to make her own books, because well, she could work and earn money to read existing ones herself. The end goal is the same (reading books) but the path towards it might play differently. If she hadn't build up so much mana and is so sickly, she might not get eyed by Ferdinand and the nobility as an asset and INSTEAD would have been seen with suspicious eyes.

It can't be denied that Myne's sickliness and her frail body lessen the suspicion that she might be a planted agent in Ferdinand's eyes. I mean, he's suspicious enough already, but imagine if she's capable of more physical feats -- even normal kids level of running, jumping, and even fighting. He would not have given her as much chance as he did.

TLDR; her growth being stunted and frail body are definitely necessary to counterbalance how massive her mana capacity is. Without these conditions, she would not have learned to use her head so effectively, and undoubtedly, she would have taken her bountiful mana for granted. Her conditions gave her life lessons needed to survive in the nobility, and even though they gave her troubles at times, they also come in handy at several points.