I mean, may be it was design choice, but I prefer illustrations to be literally on the same page or in same section as txt referencing them, if possible ....
Something can be done, but sometimes it lacks the space to let an image enter its section and the same page. This is the case of fig. 10.8 and 16.2, which I cannot fix. Latex works like this: we can give indications of where we want an image, but then it takes care of finding the best layout. It is one of the great advantages and convenience of Latex, but often the solution it finds is not good. Moreover, when you change or add something over time, the structure changes again every time you build the pdf. For example, I have arranged the figures you pointed out, but nothing prevents latex from changing their position again in the future. I have learned that the best solution is to intervene as little as possible, even if in truth I always find myself fixing something and then again and again. Keep reporting every issue, when you notice them: this finishing work is important.