Yours truly for iMore:
From Apple’s side, bringing Shortcuts support to one of their actions forces cross-platform parity, highlights the features of the app and makes them more accessible, and pushes them to be even better for the next set of expected actions.
For developers, Apple adopting Shortcuts gives them a template for how to build their own actions, gives greater emphasis on the ecosystem to encourage adoption, and also gives them hooks into the everyday default apps that people are using to tie together with their own third-party apps.
And for users, they are now able to take greater advantage of what’s possible, rediscover and utilize the features that are there, and can start to fully rely on Shortcuts as a true part of the iOS and macOS platforms.