You're not necessarily wrong, but the phrase "push a narrative," the scare quotes around "qualitative data," and your initial comment suggest to me that you are not familiar with qualitative research but have a bias or mistrust against it (no judgment, just stating my observation). If you would like to know more about it, this[1] provides a reasonable overview, and if you would like to know much more, I can ask my spouse, who is a qualitative methodologist in medicine at an R1[2], for her recommendations. I can also tell you what I think of this specific paper, but I did not want it to color my initial comment.
This is a qualitative methods paper, so statistical significance is not relevant. The rough qualitative equivalent would instead be "data saturation" (responses generally look like ones you've received already) and "thematic saturation" (you've likely found all the themes you will find through this method of data collection). There's an intuitive quality to determining the number of responses needed based on the topic and research questions, but this looks to me like they have achieved sufficient thematic saturation based on the results.
There are a few broad reasons this can happen. One possibility is that they want to know if the treatment causes suicidal ideation, and the effect is often small enough that people more likely to report those symptoms independent of the treatment confound the result. Another is that they don't want to have to deal with the safety protocols that come with screening in participants who have reported any history of suicidality. Another still is that higher likelihood of an active mental health crisis means that it's harder for study coordinators to determine if participants have provided informed consent.
Sometimes studies are specifically for treatment-resistant depression, and I expect those studies are more likely to screen in participants with a history of suicidality, so I would recommend keeping an eye out for those if you would like to participate in clinical trials.
[1] https://en.wikipedia.org/wiki/Qualitative_research
[2] https://en.wikipedia.org/wiki/List_of_research_universities_...