I don't know where you heard that but that's not true. Certainly not true with us in Belfast. Some cats who need rehomed, that have lived indoors with an elderly person all their lives, would require indoor living only as that is all they have known.
Before I got my Bella I emailed Cats Protection UK, after having been told by our local CP that I could not adopt a cat to live indoors.
I (eventually) did get an email from them, to say that their policy (in the UK, perhaps not where you are?) is that only FEV (etc) infected cats and injured (missing limb) cats will be given to indoor homes.
They went on to say that even indoor cats must be placed with outdoor homes. This is a hard and fast rule. The people I know personally who volunteer at our local CP say the same thing.
They will not give any healthy cat to an indoor home.