Checking the repotting guidelines I see:
"Bonsai soil mixture
Choosing the right soil mixture is crucial for the health of your trees, it should be draining enough to prevent the roots from rotting, while absorbing enough water to supply the tree with water. Although some tree species need special soil mixtures, the following mixture is suitable for most trees:
Mix Akadama, pumice and lava rock together in a ratio of 2:1:1. When you do not have time to water your trees regularly, choose a more water absorbing mixture (use more Akadama), while you should choose a more draining mixture (use more lava rock) when living in a wet climate. Read the Bonsai soil article for more detailed information on soil mixtures."
And checking the bonsai soil article I see
" Deciduous tree Bonsai soil
50% Akadama
25% Pumice
25% Lava rock
Coniferous / Pine Bonsai soil
33% Akadama
33% Pumice
33% Lava rock"
This is what made me think that by saying " use a normal potting soil" the guidelines on this site imply the above mixture is in fact "normal potting soil" when bonsai are concerned.
But whether I need akadama or not was not my original question