I see what you mean. I do not believe href should be used for multi dictionary search because it is highly unreliable.
For instance, “しばり【縛り】” is formatted the same in both the dictionaries you have but that is just a coincidence. The same word in 新明解 is formatted as “しばり【縛（り）】”. This mean that you won’t get a multi dictionary match when clicking on a link.
It is this way because all dictionaries do not have the same formatting, for instance:
明鏡: とらえる【捕らえる・捉える】
大辞泉: とらえる【捕（ら）える／捉える】
大辞林: とらえる【捕える・捉える】
三国: とらえる【捕らえる】
岩波: とらえる【捕(ら)える・捉える】
日本国語大辞典: とらえる【捕・捉】
新明解: とらえる【捕（ら）える・捉える】
As you can see the entry is different for every single dictionary. This means you won’t get any multi dictionary match when clicking on a href link.
For this reason, I believe that href links should not be used for multi dictionary match altogether. The purpose of a href should be a reference within the same dictionary. Ultimately the source dictionary is referencing himself, not other dictionaries. You can always highlight the word and do a multi dictionary search may the need be.