My understanding of Raquel's post is that there is one ITSP (SIP or GV isn't stated) configured on her OBi100 and there are two phones in parallel plugged into the 100's PHONE port. As she says, when one phone is in use, the other cannot take a different incoming call nor make a call.
An OBi202 can support two separate phones, ie not in parallel. With either 2 VoIP services configured on it or 1 VoIP service that allows more than 1 simultaneous call, then the two phones can be used for 2 incoming calls or 2 outgoing calls or 1 incoming and 1 outgoing.
Furthermore the 202 can be configured such that calls are handled in various ways such as:
1. An incoming call on either line rings both phones and first off-hook takes the call.
2. An incoming call on either line rings only phone_A unless it is in use, in which case phone_B is rung.
3. An incoming call on line_1 rings only phone_A unless it is busy in which case phone_B is rung.
4. An incoming call on line_2 rings only phone_B unless it is busy in which case phone_A is rung.
5. An outgoing call from phone_A always uses line_1.
6. An outgoing call from phone_B always uses line_2.
7. An outgoing call from phone_A or phone_B always uses line_1 unless line_1 is busy in which case line_2 is used.
and more.
Just because a single GV number can support more than 1 simultaneous call does not guarantee that this applies to all VoIP providers.
I have an OBi110 which has only 1 phone port, so I've never tried any of the above myself. It is based solely on my study of the Admin Guide and may contain errors.
Corrections welcome.