I understand how it can be frustrating, but it can also be super helpful.

I'm not super familiar with Ada++, but in Ada all declaration areas are the same. You can declare anything (types, functions, variables, tasks i.e. threads, or even full packages) in any declaration area. This is actually somewhat powerful in being able to write everything locally and then refactor it out to where it belongs.

Writing tasks in declarations is interesting because they operate like C++ jthreads, so the related block of statements won't exit until all threads complete. You can get around this by detaching work by using allocators, but that's more advanced.

The advantage of declare blocks would be the structure they provide - both in terms of understanding how much memory usage a subprogram can have in branching scenarios, but also as a way of showing the programmer possible areas where the problem might be better broken up into smaller pieces.

Note that within these declare blocks you may also declare new types and further subprograms - something which cannot be done within the body of a C function. Imagine the possibilities there : )