Comma before and?

As I understand it, you should only use a comma before a coordinating conjunction when it joins two independent clauses. For example,
I went to the shop, and I then went to the cinema (correct)
I went to the shop, and then to the cinema (incorrect)

However, I constantly see sentences such as this:
We’ve also had the chance to build a deeper relationship with Satya and the Microsoft leadership team, and to witness the strategic and cultural shifts they are driving.

Because the second phrase following the comma + 'AND' does *not* contain a subject and is therefore not an independent clause, it would seem to be grammatically incorrect.

Could someone advise whether there is another rule about commas and coordinating conjunctions that allows the above example to be considered correct?

Many thanks