Cache is not cleaned if the cellphone is on, a reboot would suffice that in most Android. Blackberry is different and I don't know iOS enough to tell, but they do integrate with iCloud.
Forensics have pretty strict rules. One of the assumptions and limitations is that the phone will be off. However, they're not that good in all cases. As I mentioned in my original comment, brand new phones , (and usually older versions 1 year old ones), would suffice.
The worst things Cellebrite tries to keep off hands the "evil" people (those who are already paying them enough money), will get access to the zero-days I referred to in my original reply.
Cellebrite is not that good at their job. They employ a few 0days for a few Android bootloaders, but in general most of their vulnerabilities used for extraction are either shitty or taken from the public which means if you have a fully patched Android device you're ok.
Owning a brand new IPhone 7 with SEP and encryption on would make them useless, for now.
A while ago there was a "leakage" which also included a few things which weren't supposed to be in the regular interwebs, while the files were quickly removed from their servers, a few people have managed to get what is needed.
On the other hand, remember that cellphones nowadays are quite fragile and should be used with caution regarding any sensitive information, if you have something important better keep it somewhere else, not on your cellphone.
This article is just a lame effort of their new "research", (more like PR), group manager to promote them, which he does in a perfect way, if only he had a proper job.