This question appears to be based on a simple misunderstanding of definitions.
The founding of an organisation, and the establishment of a foundation under Spanish Law are two different things.
Collins English Dictionary defines founding as "relating to the starting of a particular institution or organization."
The founding of the organisation was in 2016, and by 2017 they had created their website. The Internet Archive started crawling it in November 2017. That version includes a blog entry dated August 1, 2017 announcing the launch of Safeguard Defenders.
The registration of the organisation as a foundation in Spain's Registro de Fundaciones (Registry of Foundations) came in mid-2019, according to the link you provided.