No, the Bowser guidance says "Fight smart and look for chances to counterattack" verbatim, not even mentioning shield grabbing or grabbing for that matter, and the Yoshi guidance encourages shielding and grabbing when the Yoshi's using Egg Roll, which is the most effective strategy in such a situation (especially in online where attack timing can be screwy).
Shield Grabbing isn't "noobish" or anything like that, if it's effective for the person in question then it's effective, and if anybody wants to win against it they''ll have to suck it up because unless it's something that's considered universally over-powerful, nothing's going to change about it (unless a counter comes that beats it 100% of the time). The first tip I'd give (since I have to learn not how to just jump in front of an enemy and leave me wide open for a free grab myself) is to focus more on letting the enemy come to you and positioning yourself so when they approach you, you have the spacial advantage.