That the party of Irish home rule should reject so liberal a proposal as territorial self-determination is odd..
The whole point of the Gladstonian Liberal party’s position was that it saw home rule as a final settlement that would recognise Irish aspirations for self-government while reconciling Ireland to the union. The Liberal party certainly did not support Irish independence.
The Conservatives and the schismatic Liberal Unionists opposed home rule inter alia because they thought it would inevitably lead to complete separation while the Liberals saw it as a way of averting such an eventuality. In the end, because home rule was never tried, the failure to grant it did indeed lead to independence.
So there is nothing odd here at all about the attitude of the Scottish Lib Dems. In supporting a devolved parliament for Scotland, while resisting independence, they are being entirely consistent with the views of their Gladstonian forebears.