[deleted] Is this true?
Yes. Read this
[deleted] Can some Pixel's be more secure than others?
Yes as well. The 8/9 series are more secure than their counterparts because of a very important security feature called hardware memory tagging that is only supported on the hardware of the 8th/9th gen pixels.
The 9th gen pixel is the most secure one at the moment as it has modem hardening. Although, this could probably be backported to other devices as well but for now, only on 9th gen.
Usually the latest iteration of a phone is the most secure one.