The oldest post mentioning the HTTPS requests was back in 2021 Hide/Block HTTPS Requests, when it was just the odd request from an apple device.
But it's not just apple anymore. Android sends these requests (often directly to 8.8.8.8) often now,
They are seen from browsers such as firefox when browsing other legitimate sites too:
But, there has been more and more of this over time and it will continue to get worse as it serves as yet another mechanism helping advertisers and trackers to obfuscate where they are serving from.
For those not running another blocking server between pihole and their clients, these queries can be blocked by Pi-hole, but as seen from the screenshots above, some legitimate services may need whitelisting.
As per the link in your post, Cloudflare recommend blocking them (either NXDOMAIN or simply dropping them), likewise PaloAltoNetworks in the link in the post above) recommend blocking them.