That CGT exemption is only for Bitcoin purchased in the last financial year. Older holdings would come under a different rule.
And as for trading between cryptos? I believe any gain would be classed as income and taxed accordingly.
Best to consult an Accountant on your specific situation either way.
In your linked ATO reference, it states:
So, it would appear not just to apply to the current FY, unless I'm reading it wrong.
I would think the trading between cryptos would loose the ability to claim personal use and would trigger CGT events if you are an investor and be classed as purchasing and disposing of inventory if you are carrying on a business.
But I'm not accountant, so please don't rely on this.