VHI Insurance with pre-existing condition: what exactly is not covered?

Hello there,

I just moved here from the UK and I seem to be quite confused at the pre-existing conditions rules regarding VHI policies. I understand that the waiting period is 5 years for any pre-existing condition. But here's the thing: a few days ago I decided to have a colonoscopy directly related to my pre-existing condition at a private hospital. On being admitted I gave all my insurance details as well as details of my pre-existing condition and when my symptoms began. Everything went well and on being discharged and after a few days I received the VHI claim form through the post and to my surprise, they covered everything. So my question is: what exactly is not covered during the waiting period? If anyone could clarify I would greatly appreciate it.

Thanks.