Hi Shawn. When you use get_option() you are specifying a piece of information you wish to receive and – just in case that piece of information doesn’t exist – you are also specifying a default or fall back value.
So get_option(‘time_format’, ‘g:ia’) will not return ‘g:ia’ unless 1) the WordPress time_format setting doesn’t exist in the database, which would be very unusual, or 2) time_format itself is set to ‘g:ia’ (this can be controlled via the WordPress settings admin pages).
You’re correct that different methods are used within the plugins – there is no official answer for that, it really depends on a mixture of things such as the context, the programming style of the developer who committed that piece of code and so on.
Of course we try for a high level of consistency but now and again these things might get away from us.
I hope that answers your questions and just let me know if you need any further support 🙂