In v2.5, when you scan an alien ship there is a chance to learn tech data from that ship. If you find tech data you don't already have then you get an event and gain some tech points. In v2.6, you will now get an different event every time you scan an alien ship and learn something new about that ship, regardless of whether you already have the technology.
For example so if you scan an alien battlecruiser in v2.5 and it has 15cm Ultraviolet lasers, there is a chance you will get data on one of the background technologies for those lasers, such as Ultraviolet Wavelength, 15cm Focal Size or perhaps the capacitor recharge rate. Assuming you got data on the 15cm focal size, then if you already have that technology there will be no message and you will see no event because you didn't learn anything.
In v2.6, in addition to the above, the fact you successfully scanned the 15cm focal size is added to the Alien Class details for that ship on the Tactical Intelligence window. Even though you didn't learn anything to boost your own tech, it is still valuable intelligence to know that the ship has 15cm lasers. When you learn something of this nature a new Alien Class Scanned event appears and informs you what you learned about the alien ship. If it is also technology you don't have then you will get a separate Tech Data Scanned event as well.
This should be very useful information in determining the capabilities of alien ships beyond the existing automated tactical intelligence data.
Steve