Animation curves in the animator's additive layers

Recently switched from the 2019.4.39f1 for 2022.3.43f1 and noticed a strange behavior when reading values from animation curves in additive layers. If in the old version everything is read without problems, then in the new version, if a curve of type f(x) = c is set, then the animator seems to ignore it and constantly outputs a zero value. Can you tell me if this is a bug or a feature? Does this make any sense, or is it better to upgrade to a newer version of the engine?