I don't think that's common. Our pediatrician, who is part of a US major hospital, never mentioned this and basically said "introduce new foods on days without much going on in case you need to go to the ER."
blood tests aren't very reliable like that. i have been with my partner to the immunologist many times over the years and observed skin prick tests and seen blood test results and watched her get epipen'd after a bad prick test.
she will go into anaphylaxis if you wear a jacket you brought to somebody's house who has a cat.
her blood work says the IgE count is fairly low.
they can indicate more testing should be done, but they aren't perfect. neither are skin prick tests. i can dig up some of her reddit comments about it if you're interested.
I had a bunch of allergy blood tests after having an allergic reaction to kiwi fruit. My results came back "severely allergic" to almond and sesame, both of which I have eaten all my life with zero issues. No antibodies to any of the pollen I am actually allergic to or to kiwi. I didn't show any allergies to anything when they gave me a skin prick test either, despite having had hay fever my entire life, which was ultimately the cause of the kiwi allergy via oral allergy syndrome. The doctor basically shrugged and told me "allergy testing is more of an art than a science."
