Here is my criteria for a "unique" trick in a shred30:
1) A unique trick is 3 adds or higher.
2) A trick executed on the left side is unique from a trick executed on the right side.
3) Once a trick has been executed on a particular side it is no longer unique if executed again on that particular side.
4) A unique trick has a distinct jobs notation from any other unique trick. (i.e. If two tricks executed on the same side have the same jobs notation then they are not unique)*
*side note: I think the timing of dexes can change the jobs notation of a trick (i.e. the placement of >> in the trick) ex: ss dlo vs plo
It follows from 4) that barfly and downdoubledown are not unique from each other because apparently they have the same jobs notation. However, blurriest and blurrier are unique tricks because they clearly have different jobs notation.
I think the issue with doubledowns arises because most people do the first dex fairly uptime to midtime with a very low set. Consequently, a barfly tends to feel quite different from a downdoubledown similar to how a leggy fairy set feels different from a leggy atomic set (compare far to ss).
A legover dex on the other hand is usually done quite downtime, so a far legover doesn't *feel* very different from a ss legover.
It comes down to opinion then. Is the first dex in a doubledown uptime enough to consider it a "set" and thus unique from it's variations? If you think it does then there are probably other tricks that also need the same consideration. If you don't then the doubledown variations should not be considered unique in a shred30.
Of course the definition of "unique" could always be changed to specify uniqueness of particular tricks. Alternatively, the definition of jobs notation could be tweaked to your fancy.
I don't even think it really matters what rules are chosen as long as the rules are defined well beforehand, giving the competitors time to adjust their strategies accordingly.
