druets

It seems that Syl is unfamiliar with the yellow spren. She also may not have any intuitive feeling about them. The inception of the idea that the yellow spren are Voidspren actually seems to come from Kaladin. At least, the idea isn't given to him by Syl, as an intuition or memory of hers. Syl is not necessarily detecting or describing anything about the other spren - she may simply be deducing that these "must be" Voidspren as Kaladin is, or accepting his deduction as correct. The fact that she calls it "that other spren" implies that it is a type Syl is encountering for the first time. With the Cryptics, Syl remembered their name and something of their nature even before encountering Pattern in the Physical Realm. She also exhibited a strong feeling regarding them right away. When she first saw Pattern she could identify what type of spren he was, then remembered more about Cryptics' nature afterwards. If she remembers that much about Cryptics from having known them in the Cognitive Realm, I think she would remember something about the yellow spren if she had known them. And she almost certainly would have told Kaladin right off the bat what kind of spren they are if she knew. Some of Syl's intuitions seem to be pre-conscious emotional memories from her time in the Cognitive Realm. Those memories first manifest as immediate, visceral reactions to things she encounters in the Physical Realm, that she can't explain at first. The exact judgment she makes of Cryptics seems to confirm this. Syl calls Cryptics: This fits the biases and opinions she would have developed living as an Honorspren interacting with Cryptics in the CR. Honorspren and Liespren are contrary, and are in a complex conflict according to Jasnah, but have also fought against Odium together with their respective orders of KR. Likewise, Syl knew in the CR that most Shardblades are dead spren, and even before she remembers this in the PR, she has an immediate visceral reaction against Shardblades. With the yellow spren, she doesn't seem to exhibit an immediate visceral reaction. For the first while after encountering the yellow spren, she just seems to just be hiding her nature from an unfamiliar higher spren. The timing of her later fearful reaction implies that she may be reacting in that moment to the idea that this "must be" a Voidspren. Syl also has intuitions about things she hasn't encountered before, like when she first sees the red spren. The contrast in her reactions to red spren and the yellow spren highlights the issue: With the red spren, Syl expresses an intuition about them right away, as being "dangerous." With the yellow spren, she doesn't express or show any immediate feelings towards them except caution and maybe suspicion - and as Syl is cautious and suspicious with Pattern, suspicion from Syl towards another spren does not equal that spren being of Odium. Maybe Syl did have an intuition of her own regarding the yellow spren, and Kaladin just beat her to the punch in expressing it because they couldn't talk much. Can't know that for certain though, and at the least the contrast highlights how Syl didn't express an intuition of her own regarding the yellow spren. The yellow spren may still be Voidspren. Maybe that is why Syl is unfamiliar with them. But I don't think anything has said about them can be taken as an indication of their nature.