When he says 'by math' he means in an interview they stated there are a total of 21 trees between the 3 classes. That's 7 total, 3 of which are specializations coming out to 4 base trees. There is also 1 'extra' that you don't spend points on for the quizzy mark. Ultimately it comes out to more actual 'things' then DA2, all be it DA2 has more stuff to physically spend points on by a small amount, though as I've mentioned before earlier in the thread that was mostly on upgrades.
There was an average of 5 skills and 5 upgrades for the 9 skill 'webs' in DA2, comes out to 270 total in DA2. DAI by contrast has 4 tabs but instead of 10 max point it's closer to 14, and 5 of those are upgrades. 2H as we've seen, for instance are 5 active, 4 passive, and 5 upgrades. If every skill tree is relatively close that's 56 base 'things' to spend points on (instead of 60). However that's 40 total active and passive, opposed to 30 in DA2.
Basically, it's more focused, and has more actual skills to spend things on (not counting upgrades) but total amount of things to buy is slightly less. That said you'll get like 30 skill points to spend like the past games which means even if you have access to, lets ignore 1 tab cause weapon type, 42 + 10 for specialization (blind guess from old footage) that's 52 things to 'spend points on'. You'll still be picking and choosing and ultimately can only have 8 active skills bound at a time.
For me personally I'll be having a heavy focus on passives and only taking skills I wont use if it's required to get said passive. Plan on maxing out my specialization for it's 3-4 active skills, upgrades/passives, and have them bound while mixing in 4-5 skills from the base trees to flesh out the other side of my character. My warrior will end up with Counter Attack and all the 2H passives, might also take pummel bash depending on how useful that remains. Most of my 'attacks' will end up being Reaver based though, and ill have stuff from the other 2 trees for taunts and charging and whatnot.
TL:DR Yeah, 4 base skill trees, 3 specializations to choose from (can only take 1). 8 total active skill slots (for all platforms including PC). However the skills seem to have more tactical advantages such as Icewall and the lightning circle cage thing. Stuff that, frankly, never even existed in DAO.