But is Avanza even considered as "one entity" if in fact dozens of retail people hold the SIAF shares in that account? But you might be right. If they wouldn't be considered as one entity why would they suddenly disclose this stuff.
Avanza was non-compliant with SEC rules before the filing. Rember that the threshold for filing a 13G is 5% ownership. As can be seen in the filing, Avanza reached 5% ownership in Q4 2010