Disclaimer: This is about truly cold approaches, such as on the street or in a store. Club/bar game is a different topic and social gatherings are another thing entirely. For the duration of this post, let's imagine ourselves in a book store, and there is a girl that caught your eye in the fantasy isle. She is alone at the moment and not in a hurry.

Openers are typically divided into direct and indirect, with the direct ones being ones where you state your intentions clearly and indirect one where you obfuscate your intentions.

If you are using a direct opener, you might say something like "You just caught my eye", clearly stating your interest and implying that you found her pretty. Where does this leave you? She knows what this is about instantly. You demonstrated courage, she is probably a little flustered because this rarely happens and you can be very direct and get her number or an instant date. If she is not interested for whatever reason, she can rebuff you directly, you wish her a nice day, and don't waste each others time.

Stating your intentions was pretty straightforward and offered no wiggle room for misinterpretation. However, obfuscating them can be done in two major ways: using a pretense or commenting on the situation. Those two are very VERY different and should not be thrown in together under one label, because one of the is just stupid and lowers your success chances.

If you are using a situational opener, you might say something like "Oh, you a fan of Sanderson too? Have you already preordered Wind and Truth?" Where does this leave you? She is unsure whether you are talking to her because you are interested in the topic, or for other reasons. You both can check if there is a vibe between the two of you, and if yes, you can always ask for her number after confessing your interest - and that is important - that you could have developed throughout the conversation, not only because she is a nice piece of meat. If she is uninterested, she can make this clear without an explicit statement. Al in all, this takes a little more time, needs more creativity, but puts less pressure on both parties.

If you are using a pretense opener, you might say something like "I am looking for a present for my cousin, can you help me pick a book she will like?" Where does this leave you? With no good way forward!
Option 1: She believes you, and helps you pick out a book. And then you still keep talking to her. Why? At best, she is confused, at worst she feels you are a lying PoS and obviously a PUA. Even if you somehow manage to turn the conversation around, your first interaction with her will always be a lie. Are you always lying to get what you want? Are you a coward?
Option 2: She doesn't believe you, because she is not 16 anymore and everyone knows about PU by now. She will still help you, because she is polite, but when you inevitably ask for her number or something similar, she will feel annoyed, for all the reasons outlined above.
In the end you lied and wasted time, all for ntohing, or a suboptimal result.

TLDR: The term "indirect opener" should be retired and split into "situational opener" and "pretense opener", and the latter should never be used.

PS: There is an argument to be made that there is no such thing as an indirect opener anyway, because men just don't talk to women randomly, and everybody knows that. But there are good reasons to still try to obfuscate your intentions, and there is actual peer reviewed research on that.