No, it is not lol, and this is the typical assumption ridden opinion I’m used to from the likes of you. So very well, I’ll debunk this nonsense as well and post it to the OP:
“The Marines described Mihawk as having stronger swordsmanship than Shanks. This means Shanks is the second strongest swordsman in the One Piece world, and thus Ryokugyu cannot have a black blade because his swordsmanship is weaker than Shanks’ swordsmanship”
This argument is an extension of the “Ryokugyu is not a swordsman” argument I posted above, and there are several hardcore assumptions built into this argument that have never been proven.
1. Most glaringly, the assumption that because the Marines stated that Mihawk is stronger than Shanks, that this means Shanks is the second strongest swordsman. No. Mihawk is well known for his duels with Shanks, they are world-famous events, whereas as far as we know, Mihawk has never fought Aramaki. This line of dialogue is simply a callback to previously existing story events that we know of: that Shanks and Mihawk once regularly fought, and Mihawk surpassed him.
2. Once again, we have the assumption that achieving a black blade is directly proportional to how much of a swordsman someone is, which has never been stated. As stated previously, the two components of forging a black blade are CoA and Time, nothing else. There are swordsman in the world of One apiece (Shanks, Roger, and Rayleigh for example) who do not focus on CoA but rather CoC, which I’ve already discussed above.
3. What’s weird is that the same person presenting this argument also believes that both Roger and Shanks are stronger than Mihawk, so I would like to point out that this argument is not being presented earnestly or in good faith (like most arguments here) and is just a desperate attempt to prove an agenda. “Aramaki can’t be stronger than Shanks because Shanks doesn’t have a black blade, therefore Aramaki doesn’t have a black blade”…but this user already believes non-black blade users are stronger than Mihawk anyway, lol.