The view that “Sikhs celebrate Bandi Chhor Divas, not Divali”, is a modern fiction - Sikhs historically celebrated Divali. From Guru Amar Das onward, it became a religious celebration for Sikhs, but it was still called “Divali”.
When Guru Hargobind returned from his imprisonment in Gwalior, he was hailed as a “Bandi Chhor,” and joined the existing Divali celebrations set up by the Sangat - the celebration wasn’t solely for his return (although that probably enhanced it).
Historically, “Bandi Chhor” in the Sikh canon was used as an honorific for an individual who was considered a liberator - historic texts refer to Divali/Davali/Duali celebrations, no such “Divas” is mentioned for a holiday.
We see here a hukamnama from Guru Gobind Singh requesting all his Sangat's to come and meet together in his presence on the occasion of “Divali”. The Guru himself spells it as “ਦਿਵਾਲੀ”.