So is it made up by the bem or not?

Question

Layout

<section class="promo">
    
    
    <section class="promo__main">
      
      <!-- Текст -->
      <div class="promo__text">
        <h1 class="promo__title">Функциональное питание для котов</h1>
        <p class="promo__description">ЗАНЯЛСЯ СОБОЙ? ЗАЙМИСЬ КОТОМ!</p>
      </div>
      <!-- Кнопка -->
      <a class="promo__btn">Подобрать программу</a>
      <!-- Картинка  -->
      <div class="promo__image"></div>

    </section>


    <!-- Фон -->
    <div class="promo__bg"></div>

  </section>

Answer 1

Yes, according to BEM, you can’t say more without design.
The only thing is, I would definitely replace promo_text for example with promo_content
Ankhena ,

But the button is a block.

It is not necessary if it will not be used anywhere except for the block context.
It all depends on the situation, in general, wrapper methodology in BEM is a good enough practice.
What's with the tag? If this is a background and maybe it will be animated in some way or even there will be a dynamic background, then it's not a bad solution at all.