Conventions for beam grouping according to meter
According to accepted conventions, notes are beamed differently in different time signatures to make the meter clear and easily readable.
For example, music in 3/4 is beamed in one group of six eighth notes (quavers), whereas music in 6/8 is beamed in two groups, each the value of a dotted quarter note (crotchet). Although these two time signatures describe the same rhythmic value, the implicit meter within them is different, and so the beam grouping is different.
For irregular time signatures, such as 5/8 or 7/8, Dorico beams notes by default according to the most common practices for those time signatures.