Hi @mehak1890 - I'm so sorry for the delayed response and it seems like Brian's answer might be your solution.
In troubleshooting AI Search v Topics, it's not a bad thing for your phishing statements to go to fallback if your KB or catalog item content resolves the users question. This is why (I believe) we removed the Catalog Request topic - requests for KB content or items should be managed by AI Search and that frees you up to focus the topics on automation tasks that have very specific actions. "I want to request..." is a very generic phrase that could direct you across all your content. Given than the NLU VA is more linear, I find it helpful to balance my actionable automation tasks (topics) against content (AI Search).
In your example, "I want to request a pizza", the actionable task is to enter size, toppings and delivery address -this could be a record producer (so it would go to AI Search - hopefully genius results) or it could be an actionable topic if you integrated your ordering system. If it's an actionable topic, then all your example utterances are going to be variations of ordering, delivery, pizzas, pie and calling out vocabulary so the VA can recognize "Please deliver a large pizza with pepperoni to my house". With the actionable topic, you're making the order process easier.
That's not the same process if you were asking "I want to know the toppings for a pizza". More importantly, you want to consider when you don't want the topic called, even if the subject is closely related. For example, you might not want that topic called if the user asks "what are the types of cheese you use?" In both cases, the phrases are more information-gathering so I want the user to go to AI Search. I find that I try to come up with alternative phrases beyond "I want..", "I need...", "I want to request.." because (to your point) I would need to put those everywhere.
I also find that VA configuration is not in isolation. Yes, you have your entities and vocabulary sources in NLU. Let's say you don't have any of that configured, but you have synonyms in your AI Search profile dictionary, and your catalog items and KB articles have meta tags, descriptive text in the title and body and snippets that answer the user's query, AI Search in Fallback might win.
Fallback is not bad, it's one of my favorite features of VA - if the KB or catalog content doesn't resolve the users question, the user has the ability to contact a live agent or create a ticket, so I find getting Fallback to be very efficient.
I hope that helps!
