Sometimes I am a classicist - or just stubborn.
I never liked to pour drink ingredients into the "dry" shaker or Boston glass and after that add ice.
It feels not natural to me [maybe because I learned it a different way].
But I also believe [and tests still has to be done], that you have more dilution, as especially the glass part of the shaker can hold quite a lot of thermal energy.
Now - I was always a fan of pouring ingredients directly onto the ice. Well - off course you have to strain out the melted water before you do it.
However a couple of days, I tried another technique - which feels… quite great!
I used small tumbler, to pre-pour my drinks. My Boston glass was filled with ice and had more time to chill - also I could do different drinks the same time, without the fear of over-dilution.
Then - just before I finished the drinks I dumped the drink into the Boston glass [usually instead of straining out the melted water, I just removed the whole ice into the ice chest and scooped some new ice] and shook - off course for more than 15 seconds.
A great improvement would be, to have markings on the glass [or even better using lab tubes - maybe even made out of plastic] - only maybe every 10 ml, so you can eyeball the rest. That could give you some additional control, if you just poured right [yes - we all know, about some busy times, where you don't really know, what you did last seconds].
Additional to the obvious advantages [and the disadvantage, that you have to clean up more bar-ware], I think it has a quite advanced aesthetic - it looks quite professional, and with markings, you could even use your jigger more seldom [or you can use lab measurement cylinders].