Zelda has more range, does more overall damage, and has more knockback in her throws, compared to some other characters.
More range at the cost of a slower start-up. Seriously, the range doesn't even mean that much because many characters have enough shieldstun and push on so many reliable attacks that she can't even dash grab anyone reliably unless it's on a trip. She's never gonna standing grab a competent player out of shield because they're either pushing her too far back for the grab or they're not in 11 frames of lag AND in range for the grab to work. Standing grab will never grab anyone unless they just make a huge mistake. Pivot grab is decent as a mixup, but even then you can punish it on reaction. All of her grabs can be beaten on reaction.
You get the grab, you pummel for 3% at best (which actually rarely happens in a real match - she's almost always doing 2%... so maybe 5% above 100%), and then you throw them somewhere. You might as well pick her most damaging throw. You get a total of, I'll say to be fair to her, 17% out of two pummels + b-throw. Her throws are very bad, and we're not really gonna go into more detail about that. All she can do is U-throw and hope to U____ someone.
She has no grab releases except for, what, ground-releasing a mother boy by the edge and then keeping them there, or using Dsmash.
All of this is part of why Zelda is so ridiculously easy to deal with. She's so easy to kill if you just shield anything of hers but an Fsmash at about max range. If she's trying to grab you, you can react to it either with a fast jab or a spotdodge. Grab range is ridiculously overrated when it comes to Zelda. If you're trying to space for a grab like that, you're better off using *anything else* she has. If you're trying to grab OoS, you're better off using her amazing OoS game that doesn't involve her grab in the slightest over a subpar option like grab. Unless you can legitimately catch someone off guard and unless you suck at lightning kicking or if you just don't know when you should be using that frame 6 Usmash, frame 5 dtilt, or frame 5 Dsmash, you really have no real reason to grab with this character because of how bad it is. The fact that it's her only option against shielding worsens things even more.
Most other characters gain something by throwing their opponent somewhere, either with a chaingrab, positioning that includes more than Zelda's gameplan of "throw them up and hope to hit someone with this obvious blast of fire", or resetting spacing so they can use their good projectiles to deal with their opponents. What you say is a fact, but it can potentially completely blanket its flaws.
jack don't forget that every time you dtilt trip, it's a free grab. It's also a free grab if they happen to throw their shield up from the lock. It's also a free grab if you hit dtilt fresh at later percents before they pop up. There's a large percentage window from jab where a grab is possible straight after providing they get a hard landing and that extra lag.
At the lowest damages, dtilt gives the opponent frame advantage.
At the locking percentages... it's a lock.
In a certain window, it doesn't give frame advantage and it's not a lock. That's the only time you should really be using her grab after a trip... well, that and if you trip them right before they SDI out of dtilt's range during the lock. That said, Dsmash provides far better positioning than all of her throws, ftilt is better at the lower window area because it's stronger than the throws and you don't risk your opponent getting out after a pummel, and on some characters, you are far better off with a lightning kick.
The shielding part during the lock is more or less fooling your opponent, and it works, but if they're SDIing away from you and dtilt is still reaching, they're probably looking to jab you or to get away from you. If they're moving away, the time it takes for a dash grab to come out is enough time for them to be out of dash grab range.If they're not moving anywhere, then by all means go for the grab, but a player not moving anywhere while getting hit by the dtilt lock is likely a bad player. As for the fresh dtilt right before they pop up, assuming that isn't a trip... you're better off dtilting and having another chance at a trip.