They literally just installed
yiisoft/* package, expecting namespaces started from
yiisoft should be natural (most of packages works in this way, convention used in
yiisoft/yii2 was quite unnatural in this matter).
Also Yii 3 will not be just a framework like in case of Yii 1 and Yii 2, it will be more like ecosystem of libraries, which can be used with any framework/stack. Using framework-agnostic namespace may actually help in adoption of some packages, since there will be no confusion like “hey, I’m using Laravel in my project, I should not use this Yii library because it is a different framework”.
Actually I think it will help, since it will be easier to notice difference between Yii version used in application. Yii 3 will require different approach for writing code than Yii 2, so you need to switch context anyway - the more obvious difference will be, the less WTFs you will get.