All this being said -- and everyone has valid thots (and I fear we may have lost the OP somewhere mid-page 1) -- the very basic answer here is THIS IS A **DOG**.
Now, if we were talking human, it is understandable to want to do it in the least amount of time possible.
But it's actually a more complicated 'behavior' than just wanting fresh air.
I repeat -- THIS IS A DOG!!!!!!
marking is an important part of the whole ritual. Because when you poop you are leaving your calling card for the universe so it's IMPORTANT to put it in the right place!!!
When a dog 'sniffs' he's literally reading today's news. Has anybuddy gone HERE? Why not? Hmmm, that's old ... no ... this is new and I need to cover it up ... do I have ENOUGH? This is important!!!
And you know -- this isn't going to make one modicum of sense to a new dog "owner". but remember -- honestly first off, this is a BABY ... this pup is very young - just 8 months old. Which also means he's maturing as a male, becoming independant and aware (MORE SO) of other dogs in the immediate territory and the 'where' of it all is important.
If you give him sufficient outside time -- and he needs exercise and that time shared with you is precious -- he will eventually even out the schedule. But you can't take his 'dog-ness' away from him. It's what he IS. he's sentient ... but he has inate behaviors that are important to 'who' he is.
What a dog processes, information-wise, thru scent honestly isn't even something we humans can fully understand. They don't just know that this is the female rottie from down the block who wee'd here -- they know what she had for dinner last night, how she's feeling and that she's majorly ticked off at her owner for something!!
Dogs don't just have a nose -- they have a "Jacobsen's Organ" (between the nose and the roof of the mouth). When you see a dog lift it's head and sniff they are using this organ -- and truly they discern things from this organ that WE mere humans don't even know CAN BE known.
Now ... also realize that your dog has learned well. He's learned that this frenzied behavior WORKS. It gets results and it gets you outside NOW.
However -- if you are going to do a run line -- you may want to actually attach the line INSIDE the house (a grommet in the floor works well). Then, first, you can leash him BEFORE you open the door (some day there will be something out there he can't WAIT to get to and he'll slip right out of your hands!!). PLUS, if you need him in post haste -- you won't have to go "outside" to get to the line.
However -- don't use this all the time -- because there WILL come the day when you need him to do his business in a decent interval. Having a trigger word like "get busy" or "better go now" can be important.
I DO have a dog who goes on command, but I didn't teach him that. Frankly he was VERY ill last year and in ICU up at the University of FL for THREE weeks. He got used to going where he had to go -- because often there wasn't a student around to walk him when he had to go.
But then when he'd get home with me I expected him to WAIT until we got outside. And the first time he pooped on the floor at the vet (because he forgot and generalized that going on linoleum at the vets' was "ok";). So I started telling him before we went in "Better go now."
You can tell if a dog HAS to poop right now by feeling for a ridge under the anus -- sorry that may sound graphic but the intestine is a tube and it gets full and hard when they gotta go NOW. So I always have a pretty good idea of how 'ready' he really is and I'll say "better poop! We gotta go in and I want NO accidents!" and eventually "better poop" was simply enough to say.
I can tell just by the way he walks if it's imminent. Sorry -- maybe "too much information" but these are the things you learn.