The speculation tax we used to have has nothing to do with the 25% for speculative transactions. The speculation tax was a tax of 33% if you sold for a profit within 6 months of buying the stock.
The 25% is a special tax for speculative transactions, if you are normally managing your assets meaning just doing a few transactions each year like most "normal" people do then you do not have to pay taxes on the profits, if you are however actively managing your assets and actively trading then the profits will be taxed at 25%.
At least this is how my accountant explained it to me.
And again, this is for Belgium.
This is if you are self employed business owner.
Not sure what the taxes are for people trading besides their day job.