BLOB data imported from file is not typed BLOB but TEXT.
We can replicate by following way.

1. create table

    CREATE TABLE 'Sample' ('ID' INTEGER, 'Image' BLOB, PRIMARY KEY(ID))

1. add new record on "Browse Data" tab
2. update 'Image' data by importing image file(e.g. jpg file) on 'Edit database cell'
3. query type of 'Image' data, and get TEXT type

    SELECT typeof(Image) FROM Sample

Maybe, the reason of this issue is DBBrowserDB::updateRecord(sqlitedb.cpp) method.
Imported data for update bind by sqlite3_bind_text without reference to actual (or estimated) data type.