The photos attached to your query don't look like typical fungal decay, although it's hard to be sure from viewing an image. The surface 'growth' actually looks more like the result of exposure to salt water - compare your image with the one on this site: https://www.researchgate.net/figure/Characteristic-damage-to-treated-wood-caused-by-salt-a-Treated-deck-boards-exposed-to_fig1_316317038.

There's a good explanation of acclimatisation of flooring in our Technical Design Guide #09, available for download free of charge via this link https://www.woodsolutions.com.au/publications - refer pages 33-35. Note that you need to have some way of knowing when the flooring has reached an appropriate moisture content, or perhaps it will already be at the right moisture content, in which case there is no need for lengthy acclimatisation. Either way, testing with a moisture meter will tell you when it's ready to install.

The images of your American oak flooring, sent separately, show brown stains in conjunction with 'checks' (fine surface splits). American red and white oaks are prone to developing checks during drying - fine checks may even appear during carefully controlled kiln drying. In our opinion the brown stains associated with the checks are tannin stains. However, tannin stains don't appear spontaneously, they occur when naturally occurring tannin is dissolved by moisture and brought to the surface.