I can't envisage it being legally relevant whether legal work is done in-house or not. - credulityThe articles within the link provided, summarize some of Glen How's legal accomplishments in Canadian civil liberties and various other Canadian laws involving religious activities.
While it is stated Glen How's work on behalf of JWs benefitted them, it is not clear if he or his firm was retained by WT at the time to represent their interests in those various actions. He may have acted on his own as an independent lawyer. As a practising JW, he had a vested interest in laws which impact a person's freedom to practice their chosen religion.
So too with legal matters in other countries, is the firm retained by WT to represent them, or is the firm 'technically' acting independently from WT, even as their main office is located at the Canadian WT branch?
In law, it comes down to evidence and what may be proven in court.
... to present itself as a neutral and commercial law firm, when it is nothing more than a legal front for WTS, its sole client. - credulity
I don't recall claims of being neutral. There is substantial info on the firm's website to suggest it is not neutral but very biased towards JWs.
Is WT its sole client, or does the firm possibly also represent other JWs that might need representation in religious matters?
Legal representation may include matters such as involving JW parents defending against a court order forcing blood for their child, a child custody action against a non-believing spouse, or congregation elders defending their actions after child sexual assault was reported and they had forced the victim to meet with the accused.