Similarity in vocabulary is the tool of the non-trained linguists looking to find "connection" between languages and/or dialects of the same language. This is a mistaken path to take.
As an example, 60-65% of English vocabulary is French in its root, going back to the time of the Normas. Despite this, English is a Germanic language not a Romance language (like French), because it is the grammar and the structure that determine the affinity of tongues not vocabulary. Likewise, Azeri and Turkish overflow with Persian words (or Arabic words that come through Persian). And yet, Azeri and Turkish are Altaic languages not Indo-European like Persian is. The fact that nearly half the literary Persian words are also Arabic in their origins has never reclassified Persian as a Semitic language (like Arabic). Vocabulary should almost never be used to determine affinity between languages and dialects, as it can be very misleading.
So, what if this dialect or that dialect of Kurdish contains a lot of similarities to another dialect? Again, it is the grammar and the structure that needs to be examined. Such examination, however, is the domain of a trained linguist, who has gone through systematic training, done many field works and has collect data to determine the exact connection (or the lack thereof). The sources available to us today show that the Pahli/Fayli and Silakhuri are of the same Laki dialect group, and are bridged together by the subdialect of Biranawandi. One needs to know the grammar and the structure of Biranawandi subdialect (spoken in Harsin, Nurabad and Sahna, as well as the neighbouring areas) in order to realise the connection between Silakhuri of Lakistan and Fayli of Pahla.