Reminder: Sage Advice is not gospel, but simple suggestions on how a DM might interpret things based on RAW, RAI, and RAF. The wording of the spells is such that either reading could be interpreted, and RAI is that the DM chooses. My interpretation is that if the player was supposed to select the creature(s), it would have actually said "the player chooses a (beast/elemental/demon/whatever) creature, and a number of them appear based on the CR as follows:"
On the other hand, I like getting PC input on the decision, because I want to know what they're looking for. If they specifically need something that flies, I'll try to give them a flier. If they want a brute, I'll give them a brute. If they want something to slip in somewhere unnoticed, I'll try to give them that. The main reason I don't always give them what they want, is because I may not have it conveniently available (we play on Roll20, and I don't have everything programed in).