The article you posted starts out with misinformation about B12 so I can only assume that the remainder of the article lacks credibility in other areas. Here’s the truth about the B12 content of spirulina -
" Spirulina: Not a Vitamin B12 Source
For a long time, spirulina was considered a vitamin B12 source. The vitamin B12 level which it showed when tested by conventional methods has been disproven by recent testing, which proved it to simply be vitamin B12 analogs.1-3
In actual fact, the vitamin B12 content has been measured to total just 30%, a very low amount compared to the level of pseudo-vitamin B12.4,5
As expected, taking spirulina significantly worsened the B12 status of a research group in a study carried out, which found that the B12 analogs impaired the absorption rate of genuine vitamin B12.6 Vegans, vegetarians and people with vitamin B12 absorption difficulties should thus steer clear of spirulina products.
It is also not recommended to take spirulina alongside vitamin B12 supplements, as the pseudo-B12 in the spirulina can hinder absorption."