Does a stronger engine always play better than a weaker one in every position?
Not necessarily.
The accurate way to understand "stronger" is "performs better in more positions".
For example, if a is stronger than b, a may perform better in 60% of positions, about equally in 10%, and b may perform better in 30%, yet a is still stronger than b.
That a is stronger does not mean a is a complete superset of b.
Even the strongest engine today is worse than traditional engines, or even humans, in some positions; it is only a matter of how many.