That’s a poor excuse. The fruit was regarded as a bigger deal than a Yonko, so why should Dragon being suspicious about the WG wiping out his son be an issue to them in the slightest? Are you suggesting that Dragon would somehow magically intuit that it was because of a devil fruit that secretly got its name changed that they have been hunting for 800+ years?
They should consider the possibility of Dragon becoming suspicious about a secret he can do nothing about to be a bigger issuer than the actual fruit itself?
All you’ve done is just point out why it’s all the more problematic that the son of their current greatest enemy is running around with the fruit of their original greatest enemy.
And this is beyond pretending to be obtuse: when have they ever gone after Luffy specifically for his fruit? Please take as much time as you need…
Its not a poor excuse. The fruit was unawakened in the hands of a rookie they probably felt good about crushing, so they sent people after him on multiple occasions, whether it was about the fruit or Luffy is irrelevant (to directly address your last point). It doesn't matter
why they were going after him, it has no bearing on the act of catching him or him getting away. The reason doesn't help or hinder Luffy's eventual escape. They sent people after him, that's all that matters.
As far as Dragon goes, what i said doesnt make it more problematic. He's not a moron, if he recognizes that they're targeting his son for any reason other than the ordinary, especially if its dangerous to the World Government, hes not going to sit back and let it happen. He will have intervened. Not to mention that he's running a clandestine organization, which makes it obvious to them that he would have spies in place, which means it would be more likely that he would find out about any overt action on their part as it pertained to Luffy.