This became quite a long reply, apologies in advance.
Lightning speed has never been an issue in NNT though?
Arthur suprised by Meliodas breaking the sound barrier along with Gilthunder and Hendrickson being pressured and tagged by said attack.
The implication here being that non of their attacks beforehand were at faster than sound speeds...
Along with many other feats which don't exactly support "lightning timer"
scaling within NNT.
Like yeah, I get it, Meliodas reacts to lightning and counters it, but it's almost as if Nakaba doesn't realise what that entails. The fact he thinks breaking the sound barrier is at all relevant should tell you that, but there's more, like how they don't perceive minutes as
much much longer in their perception. Remember Zeldris vs Ludo? Where Zel couldn't do shit for 1.8 seconds? That should have been the end of it right? Someone who should scale massively above a lightning timer would perceive 1.8 seconds as ages, not as 'instant' or see 0.8 seconds as 'mere' (stated in the scene itself) and Ludo only got one attack off.
Timed feats in NNT didn't see any improvement, there was a timed feat in the earlier chapters, Mel, Ban and King vs Dawn Roar and then another one later in the series, Zeldris vs Ludo.
Both were in the deciseconds to seconds range.
So what does this leave us with? Exactly what I said. Fan calcs and scaling. Because no actual
feats will come from the manga itself. Nakaba is just a lazy writer with stuff like this. Same shit in Kongou Banchou too.