A competent team can win from anywhere.
Of course. But like you say in the next sentence:
There are sometimes more advantageous spots on some maps for certain modes
That's putting it lightly. So let's just put it out there that the modes in question are Trials and Control.
These 'advantageous spots' aren't just sniper perches with decent lines of sight. They're entire sections of the map that lack counterplay due to limited and predictable entrance and exit points (ie: funneling doorways/tunnels), terrain/structural height differences (grenade throws are easier downhill, head is more visible) and imbalanced distances to points of interest (heavy spawns and B points).
And they're all dependent on a spawn location.
Not to beat a dead horse but Firebase Delphi for instance. Say two teams of equal skill spawn in on FBD Control. One side gets A, the other gets the dreaded C point.
About 10m from the A-side spawn they have a fire lane around 25m long in which they can look into B, move around comfortably, pickup special ammo and retreat to two different sides. One being outside, the other being back to the original spawn spot which is blocked from easy view by a crate near the door, this leads to two more exits: the giant opening center door or the back tunnel of A-point.
Pros:
Clear line of sight into B with room to move from grenades and two sides to retreat away to if engaged on.
Fastest access to B-point.
Visible special ammo spawn
Crate near the entrance to B-point provides cover for heavy against anyone in B central ring.
Pillars and center crate act as cover for anyone who has aggressively pushed into A zone from B central ring or outside.
Your very own escape route via tunnel, bringing A side to a total of 4 different routes.
Cons:
Now on C side they have a 3x2m room right off from the B-point central ring that has two doors, one in which they can look into B from and another which leads them to their inside area which is identical to A-side but without a back tunnel and an exit that's over a wall/down a flight of stairs.
Pros:
Easily accessible roof to fire into window of B central ring, curvature of roof provides great cover.
The entrance into C-side indoors has a flight of stairs and a crate
Cons:
The entrance into C-side indoors has a flight of stairs and a crate...
Main line of sight and entrance into B-point is a 3x2m room that's extremely vulnerable to grenades.
Longest distance to B-point
Special ammo spawns in the very outside back of the map while the fighting takes place near the center.
B central ring entrance room provides line of sight with C side heavy spawn.
C side heavy spawn is about 40m+ from their spawn spot. In comparison, A side is around 10m.
Only 3 different routes to and from C indoor room.
Now you could say, can't you just flip the spawns? Yes. But what if you can't? Unless a person from C side is weighing the spawns in their favor by being isolated near A side or by A-team being too close to C-side, A-team will still keep spawning near A.
Two teams of equal skill, one starts at A, one starts at C. A will win which means it's not balanced. Essentially, B doesn't matter. Hold A and control the game, that's a fine objective, unfortunately one team already starts at A-side. And that's just one map, Blind Watch is just as bad or maybe even worse.
So TL;DR. Maps aren't balanced. Employee is either lying or just ignorant, either way, that 1% of perfect balance is a bullshit claim and I wouldn't trust anything else he says just because he's 'official'.