I have a suspicion because if the info got to Dems/in the public it would damage the prosecutors’ cases that are being investigated. Giulian went to Ukraine and got probably most or all of this months ago.
Delivering the info to Washington could mean the DOJ but it could also mean testifying to Congress/Senate which would have been a very bad idea.
This is just my supposition; related to why Fitton has to wait for FOI info, because evidence directly connected with ongoing criminal investigations cannot be made public until grand juries are finished, as far as I know about anything. Legal guys can check in.
Of course what Giuliani obtained cannot be used for prosecution. The point is that access to evidence that could be used to prosecute was successfully blocked - and may still be.
You asked for proof that such access was blocked and I provided that. Perhaps AG Barr or an assistant was able, under some legal umbrella, to travel to Ukraine and obtain permissible legal evidence against the Biden's and ??.