I noticed that my my18 superb still gets some odor from outside  into the cabin while in recirculation mode.

My older my14 octavia was not getting any smell from outside when in recirc. mode.

I wonder if this is a new approach to prevent stale air inside  or does my car have a malfunctioning recirc. flap?

I am facing the same issue with my Octty. Please let me know if you found anything regarding that.

You will always get outside smells in the car, even in recirc mode.

A car cannot be hermetically sealed.

 

Eventually you would become drowsy and suffocate, so there is always a fresh airflow, just greatly reduced by using the recirc button.

But thats the reason why in Skoda's manual it says that shift to auto mode when the side windows starts to collect mist. In the manual it says that recirculating mode should completely prevent the outside air entering the vehicle.

In that case the manual is misleading.

It cannot completely prevent outside air entering the car.

 

It would be like having your head inside a large plastic bag IF it sealed completely.

 

The rubber seals around your doors provide a watertight seal, not airtight. Also, I believe, many modern cars have airflow that cannot be blocked completely using the recirc button so that the cabin air remains fresh.

 

 

 

 

The recirculation function should transfer all incoming air through your pollen filter. You can replace the filter to one with a better quality of filtration. Something like the Mann frecious plus range to aid with removing smells. This type of filter will need to be replaced more frequently to keep the cabin air filtered to a higher standard. 

There is also an issue where I set the upper blowers to throw air but even then I can feel air blowing on my legs while driving. I thought there might be a sealing issue with vents.

Take a look at the "air quality sensor" (G238 to be confirmed), it may need to be replaced. This sensor sis mentioned ins Self Study Program #107 for Skoda Superb Mk3 Part II

Have a check with VCDS, if there is a fault code related to this sensor...

Is there a diagram anywhere of where the air qualuty sensor is? ( even what it looks like) Mine's giving an intermittent error code.