@NiceGerbil
Girls before puberty, women with some types of coil, Pg women etc don't have periods.
And even then it would be people who have periods and men who have penises or similar
To be fair, they don't talk about causes for IDA in either pre-pubertal girls or boys.
For women with a coil that stops their period, they could be thought of as "women whose periods have stopped [for a long period of time, including the present, but not necessarily forever]." The important thing is that the blood loss of heavy periods is not going to make them deficient in iron (at the present time).
They addressed pregnant women's most frequent cause: "In pregnancy, iron deficiency anaemia is most often caused by a lack of iron in your diet."
They might just be trying to give some basic information for some of the most common causes, and hope that people will get an explanation for their own specific situation from their doctor.
And I'm sorry if it sounds like I'm arguing with anyone- I don't think the page is an example of the best, clearest information ever! I just don't think it is trying to be woke (as NiceGerbil says, it would then read something like "in people who have periods IDA is commonly caused by heavy periods. In people who don't have periods IDA is caused by [...]" which is quite the mouthful.
But it does show how important it is that medical information (which is often needed by people who feel ill, tired, or in pain) should be clear and easy to understand.