It appears that Matthew 26:31 is not showing up in the tool as Zech 13:7.....there is a possibility I am not using the tool correctly, but I don't think so.
Oddly enough, footnotes in the Bible translations I checked fail to mention Mt in the reading of Mk all mention Zech the ESV adds Jn. I will be interested in the comments from others.
I believe this is a tagging error in the browser dataset.
The source of this information is: Jones, David A. Old Testament Quotations and Allusions in the New Testament. Bellingham, WA: Logos Bible Software, 2009.
and that does show the verses linked:
I think it is an omission in the OT NT Tool.
I essentially made this same observation last July:
https://community.logos.com/forums/t/191692.aspx
Sean Boisen responded, saying he would create a case. Looks like no progress.