The short answer is ‘not necessarily’.
The longer answer is that the question mark was a foreign import and was not recognised in official documents until a few years ago (read more about this here and the official documentation on page 18 here). Still, it has been used in a variety of contexts for decades.
Basically, as you seem to have picked up, sometimes Japanese can feel ambiguous in writing as to the intended meaning. This is often the case when there are multiple possible intonations which can’t be clearly shown in writing. In those cases it is permissible to use a question mark. Still, it is not something someone has to do, and it is also something you’ll still see mentioned as something to avoid in very formal business communications by some people (basically, just rephrase it if needed).
These days it is very common to use question marks in all sorts of contexts, though. In texting even the use of Japanese periods (。) itself is avoided since it can seem overbearing (a concept called マルハラ, and similar to how millennials and gen Z tend to write messages in English). Question marks convey the intended intonation and soften statements.
You can read more about this sort of thing here. In essence, there are times where many older people would use a period but younger people would use a question mark. Younger people seem more likely to use question marks to indicate intonation (this is how I use it outside of formal emails as well, personally). The main conclusion being:
おそらく現代日本語では、“？”の指し示す意味が、「疑問」から「文末の音が上昇すること」へと変化しつつあるのではないかと予想されます。でも、多くの人にとっては、こういうのはどうでもいい問題なのかもしれませんね？
It should also be pointed out that in context a lot of this ambiguity goes away (and obviously in speech the intonation is different).
