Here is what I am thinking:

1) The word "official" has to deal with understanding. It does not always mean reality.

2) The word "technical" has to deal with the exact meaning of something. This means reality.

Oficially having a girlfriend means that the boy has a person he can call as his girlfriend. In his mind he thinks that she is in a relationship with him.

Technically not having a girlfriend can mean that his girlfriend is unaware that he is her boyfriend.

In reality, they are not in a relationship.

It takes two people to be in a relationship, but in this case only one person thinks he is in a relationship. The other person is not fully committed.  

  It is a sentence which shows that a  person  is not committed to something specific.

 Such a person  is someone  who claims to have a specific friend, but will also find other

friends when possible.

 Such a person   is an unstable person,  and not to be trusted as a friend, because they cannot commit to any specific person as a "friend".

I think it is easy, those people are in a relationship but they are not together very often, so they can meet very rarely either because of work or other reasons, so it is not technically possible to be together and they seem as if they were single.

when I saw it,I just remembered this sentence:

My husband died.I m sorry,in theory :P (from Desperate Housewives)

Hi Tuan,

Thank you for your clear explanation. :) I understand.

Thanks a lot.

Btw,it's NOT about myself. ;)