I have still to understand if this statement is true or not, or to say better I cannot agree or disagree with it because i went near completist with both my actual playthroughs.
So I have still to try it, but my question to everyone who has tried a fast-playthrough is: even if it is technically possible to finish it, doesn't the game feel awful if you don't do almost every side-quest? I mean, if you want to get inquisition perks you have got to raise influence and to raise influence you have to complete way many side quests. Another options is to buy influence but the problem is the same: considering that piling up money is very difficult in this game you'll have to find tons of loot to sell, and to do it you have got to explore.
If you don't explore you cannot upgrade potions, tonics, craft armors and weapons. And again, if you want to buy good resources/items you need money. So is it really fun to play without Deft Hand, Fine Tools? Or without the dialogue perks which give you some specific dialogue option? Or without the Forward Scouts perks which reveal everything on the map? Doesn't your character feel dumb with the basic gear which provides simple loot?
Here is why I have still to figure out how is possible to detach side quests from the main game and how I can do it without making my game awful.
Disclaimer - I play on casual for the first few characters and then move on to normal. Not interested in nightmare play.
For me, every character I have is different. I've finished 2 and have a couple I'm jumping back and forth with. I don't do everything but I've done enough to get the perks I'm interested in especially Deft Hand, Fine Tools. I make my armor, weapons and haven't had any problems with my options.
I always do just about everything in the Hinterlands, Follow Mire and Crestwood, mostly because I like them, but after that it just depends on my character. If there is something specific they need in an area, they go in get it and leave. So far they have all helped Varric with the red lyrium but have not necessarily done anything else in whatever area they need to go to help him. I've killed 2 dragons and maybe in future games I'll kill more but it's not a priority for me.
My mage elf (first character) actually did a lot of the missions and explored all of the areas at least a little. She romanced Solas and was super interested in eleven history and felt all mages should be free. She was also interested in Shards, but not to the extreme so she picked up shards that were easy to find and didn't bother with all of them. She went to the Forbidden Oasis but only went into one of the rooms. She felt finding the Warden history was a good thing so she looked for them if she was in an area that was reported to have them. She wanted to help Solas so she did and she wanted to help the elves so she did. She didn't agree with Viv so did not talk to her often and did nothing for her. Other than Inquisition missions, what she did, depended on how she felt about the person asking.
My Qunari rogue was curious about Qunari life so spent a lot of time talking to IB. She ended up romancing him as a lark and he made her laugh. (me too). She liked Viv so helped her. She didn't trust mages, didn't really care about elves, though she liked Sarah and respected Solas. She wasn't interested in shards so didn't even go to the Forbidden Oasis. She helped Cass and if she was in an area for something relating to the inquisition, might help out someone along the way. She would do Inquisition missions and if something else was close by she would check it out but didn't often make special trips to places.
I am having a great time doing it this way, though I'm pretty sure I will eventually have someone who has to complete everything possible.