How to handle Qualifying Deficiency question

We have a purchase agreement for an Illinois property where we waived the inspection, and is "as is". They had inspection done in March. Their inspection revealed items that we negotiated that needed to be fixed. After the purchase agreement, we did a home inspection and they found that the tile floor grout leaks the water from the shower into the basement.

Our Realtor said that we cannot use the inspection to disclose we know this and have to wait for the walk through 48 hours before closing even though this is certainly a Qualifying Deficiency.

Does that sound right?

How can we best handle this?

Honestly, I want to discuss this with them and give time rather than 48 hours before the closing. But if its the case, we wait, I want to see how to best handle this.

This is an excellent sub, so I am coming to you all.