Why do you consider this sneaky? Seems straightforward to me.
Hardly sneaky when it lays out the other things that are covered in the other versions. Did you upgrade, no, hardly sneaky enough to fool you then.
Since I never click the More Information button in alerts I never go anywhere near there.
I’m not the least bit interested in the other versions and no, I didn’t and won’t be upgrading.
Then there is hardly any sneaky attempt to get you to upgrade if it didn’t get you to upgrade.
Relax, your avast! just saved you from a virus.
Protect yourself against other types of threats by upgrading now.
It’s a sneaky scare tactic and some people who get the red popup, click on details, read what it says might be afraid to not upgrade.
There are other threats which aren’t directly related to viruses and they are being highlighted, if the user has this covered by other applications then no problem.
Some may not even be aware of other threats.
So david in a nutshell.
Are you saying that there are certain types of threats that avast free does not detect?
I know no av is 100% at detection but this implies that the paid version protects more than the free.
Have you visited the link that -midnight posted as it is showing elements that aren’t in the free version, firewall, VPN and Safe Zone, etc. Now those may not be directly related to malware threats, but could be a threat all the same.
So do you need the additional protection over and above that avast free gives.
Again, sounding the alarm bells. Nothing sneaky at all.
If you want the extra protection, then pay for it or, get that protection for free from other sources or, do without that protection
if you think it’s not required.
Your choice and therefore not sneaky at all. 
@Arnold72, are you satisfied with David and Bob’s answers? 
Yes quite satisfied with those responses.
Good