Really? I dont think so at all, dragon Kaidou just had minimal bleeding from G4 wasnt it? Luffy succeeded in putting Kaidou down for a few pages? A few minutes if we're being generous? And then Kaidou is back to the rumble without any visible injuries, i think Regular Boundman (no Penetration Haki) lose in every aspect compared to base Kaidou. Though Compared to BM, well Boundman fared better in WCI against BM i guess.
Except if you mean G4+ Penetration Armament, but it hasnt even been shown yet so...
I mean barrier haki G4 not internal destruction/penetration.
Luffy completely sandbagged Kaido and was only hit by Kaido in Boundman when offguard due to BM's sneak attack, and managed to tank it fine.
Current boundman
without time limit could just keep gattling and fucking up Kaido without Kaido being able to do much in response.
Kaido still has the bruises and lots of the damage from that time, he is just a freak at damage soak and regeneration.
Luffy's speed, defense and brute strength in this form are better than Kaido, his only issue is overcoming the regeneration, but given infinite time limit in this form that would be overcome, he does however have that time limit, which is why he needs internal destruction to overcome the regeneration more effectively.