According to the About the Project [1] section of the page:

> All film materials presented on the 35mm.online platform meet the requirements of WCAG 2.0 - they have audio descriptions, transcriptions, subtitles in Polish and English, as well as comprehensive descriptions. For foreigners, the entire film library of the Platform is available in English.

So I assume that this one also has English subtitles. The icon below the film is only about the available audio language options.

Edit: Just double checked and yes, the English subtitles are available for this one (and all other films).

[1] https://35mm.online/en/articles/about-the-project