Feeling of the single fin

Hey guys,
after years of slow progress I'm now ready (at least I feel) to think about fins.
I've read Jaffa's post on fins which is great. But there's something I'd like you to explain, a part from tech details.
Up untill now I surfed my allround longboard with a 2+1 set up, exactly as it came out of the shop.
I kept the side fins because I wanted to be able to turn the board easily and my understanding was that the single fin would kind of lock/block the board more. And I felt alright, and I learned the basics.
What happened recently is that I got a noserider and put a single fin on. I can walk on the deck and I want to progress this aspect.
Since conditions in QLD have been constantly bad, I used it only once so far but I got a good feeling.
Then I got a new 7.6 (when there's no surf you buy stuff!) to go the opposite direction: more carving and fun turns. Same here: I can do it and I want to progress this part as well.
And the guy at the shop told me he would use it with a single fin.
I was confused.
He said:
"The thruster make you turn tighter, but the single fin is more loose."
Now, English is second language and surflingo is 4th language.
I still can't really understand "loose" here.
Loose how?
Can someone elaborate?
Thanks.
after years of slow progress I'm now ready (at least I feel) to think about fins.
I've read Jaffa's post on fins which is great. But there's something I'd like you to explain, a part from tech details.
Up untill now I surfed my allround longboard with a 2+1 set up, exactly as it came out of the shop.
I kept the side fins because I wanted to be able to turn the board easily and my understanding was that the single fin would kind of lock/block the board more. And I felt alright, and I learned the basics.
What happened recently is that I got a noserider and put a single fin on. I can walk on the deck and I want to progress this aspect.
Since conditions in QLD have been constantly bad, I used it only once so far but I got a good feeling.
Then I got a new 7.6 (when there's no surf you buy stuff!) to go the opposite direction: more carving and fun turns. Same here: I can do it and I want to progress this part as well.
And the guy at the shop told me he would use it with a single fin.
I was confused.
He said:
"The thruster make you turn tighter, but the single fin is more loose."
Now, English is second language and surflingo is 4th language.
I still can't really understand "loose" here.
Loose how?
Can someone elaborate?
Thanks.