Just loaded up a snapshot world with no datapacks, and the game log is definitely inaccurate. When I use /reload, it tells me:

15:28:39.432 Reloading ResourceManager: Default
15:28:39.978 Loaded 7 recipes
15:28:40.076 Loaded 927 advancements
15:28:40.383 Loaded 71 advancements

There's 927 advancements in the default datapack, so that part's right, but there's way more than 7 recipes in the default datapack. The log doesn't mention loot tables, structures, or tags at all, and there's somehow an additional 71 'advancements'?

Loading up a world I had on hand with datapacks that include additional recipes, predicates, loot tables, structures, functions and tags, the recipes from that datapack are not included in the count (it still claims only 7 recipes are loaded). The functions and predicates from the datapacks are not listed at all, and while the first advancements number remains accurate, the second...I don't know what that's counting at all, because the number changes, but not by the same number as anything contained in the datapacks.