Never stated that in any presser. The only time that "additional video" was used in any context whatsoever in a press conference was the 4-22 press conference. The context was that they had already released two snippets previously and the video they were releasing that day - in conjunction with that press conference. From Galadriel's excellent transcript:
Female Reporter: When you released that new video, what –– if it's new,
what do you want the community looking at in that new video?
Assistant Chief Kevin Johnson: It's just additional footage of the suspect
moving around within the church. We're just hoping that somebody will see
something that piques their interest and spurs their memory so that they
may make a connection to somebody that they know and they can provide
us that tip.
And further on in the transcript ...
Female Reporter: Because it looks like the person was in there about a
half an hour. Do you know what they were doing during that time?
Assistant Chief Kevin Johnson: We do, and the videos that we've
released and the additional video reflect most of the behavior that we know
about that took place inside the church.
These are the only times you will find mentioned and in both instances Kevin Johnson is talking about the video they were releasing at the time of that press conference.
The only thing we have from MPD concerning additional footage was a question posed on their facebook page on 6/30 or 7/1 and answered twice, the second answer contradicting the first, and has since been removed from their page: