Yes, if you directly project the measurements onto a model of the globe earth, then it will directly fit. But flat-earthers are right if they say, no one is carrying around globes for navigation, everyone uses flat maps.
But they would have to concede the flat maps have errors! But the Flat earthers deny there are errors.
If the earth would be flat and you would assume a globe you would end up with a completely distorted globe.
The ‘tape measurement’ system does not assume a globe.
If we started with Lat/Lon coordinates and inferred a distance from that, assuming a spherical surface, then that would be ‘assuming a globe’.
I don’t know if you are confused yourself, or whether you are trying to represent the arguments of a person who is deeply confused!
It assumes a globe earth in the moment you transfer your data on a map.
It's easy to see. Let's assume two groups of surveyors are starting at the same point. And they do their triangulation measurements along two different directions. And the angle between the two directions is 60°. Now the proceed like this for 1000km. After that both change their directions by 60°. On a flat earth they would now meet after 500km under an angle of 0° degree. And all the points they measured would fit together to a nice triangle each side 1000km long, all angles 60°.
And on a globe?
They would first proceed along two great circles that intersect at the starting point under an angle of 60°. After 1000km they would change their direction again by 60° to approach each other. But are they now following the same great circle? No, at a distance unequal to 500km they would meet under an angle unequal to 0°, because they are following two different great circles. To meet in a straight line on the same great circle, they would have to turn by a bit more than 60°. But anyway, they would not meet after 500 km, because also the initial 60° angle was wrong.
You see, in the whole procedure of large scale mapping you have to take into account, what is the shape of the underlying surface. Only on small scales you can neglect it.