41% of newly approved drugs had 1 PhIII trial - FDA says this should be rare?

Earlier this year, the FDA put out this report:
2018 FDA New Drug Therapy Approvals
Hiding out on page 18 is this little gem where they state that 24 out of 59 drugs (41%) were designated as Fast-Track.  That spurned this great article from Zach Brennan at Endpoints News:
Almost half of all new drug approvals in 2018 relied on one clinical trial

Now the question is, if half of the new drug approvals came from only one trial, while at the same time the FDA states that one trial approvals should be a rare exception, what explains this conflict?

Maybe there are just more applications for diseases with no current standard of care?  Or maybe the FDA just has a funny definition of rare.  They also stated this in their report - 73% of applications were given priority review. 73% sounds more like standard review than priority to me.