I seen some bassmaster pros using a mh fast action for baits like a whopper plopper. Isn’t it uncommon to use a fast action for a bait like this and more common to use a moderate action

I'd say yes. I'll also say that one rod's fast action may be closer to another's XF or MF, so it's a little subjective. 

20 minutes ago, BrianMDTX said:

I'd say yes. I'll also say that one rod's fast action may be closer to another's XF or MF, so it's a little subjective. 

Exactly!  As I posted in another thread about 2 M-XF spinning rods from different companies.  It is very obvious one has a much softer tip although both have the same power and action rating.

I have always used a fast action rod for topwater, with a few exceptions.  Most companies that assign lure recommendations to their technique specific rods have topwater, in general, as a fast action type bait> Loomis, St.Croix, and Megabass all fall into this train of thought.  

9 minutes ago, new2BC4bass said:

Exactly!  As I posted in another thread about 2 M-XF spinning rods from different companies.  It is very obvious one has a much softer tip although both have the same power and action rating.

It’s clear as mud! 
 

I would hope that within a rod manufacturer’s product lines, that the various actions are consistent. They certainly are not between different manufacturers. The standard is no standard!

8 minutes ago, BrianMDTX said:

It’s clear as mud! 
 

I would hope that within a rod manufacturer’s product lines, that the various actions are consistent. They certainly are not between different manufacturers. The standard is no standard!

Gets even better when you add in power.

 

Dobyns is the main 'culprit'.

3 power spinning - named Medium - and it lines up closely with other manufacturers medium power

3 power casting - named Medium-Heavy - but it STILL lines up with mediums from others - nearly the same lure/line ratings as it's own 3-power spinning

 

Why is one 'Medium' and the other 'Medium-Heavy' when they're close to being the same power?

 

This is why I ignore the 'words' and only look at the stats - my Fury 703C is used where I'd use a medium, and my 704C (Heavy) is used where I'd use a medium-heavy.

 

There's no standard, even internally with a manufacturer.

I use MH rods on topwater lures all the time. If I am making a long cast with stretchy mono, I found that M rods or moderate action rods are too soft to make a solid hookset, especially when the bite happens far away from me. But if I am using braided lines for topwater, that's a different story.