Most people aren't in a position where playing 6h a day 7 days a week bare minimum plus split runs and whatnot is considered normal or fun. There's a huge chasm between world top guilds and "average player".
Also "getting content done" for example old raids for blp is way way faster if it's a scheduled guild activity than when people have to pug, pugs have the tendency to take ages to form, ages to replace people if they drop out and sometimes even disband if wipe happens. A guild made run will have no downtime and no wipes. So playing the same "loads" will net you more blp per hour than for a player who is on his own. I doubt many non-hardcore guilds plan old raid runs for blp, so it's not even a case of being guildless, majority of raiding guilds will just run hc tos or / and mythic and that's it.
I'd also wager an average player is vastly less skilled and less efficient than members of world top 5 guild, so any activity will take him longer because he's not as well organized, does less dps, has worse knowledge of the game and so forth. So things like "farming argus rares" or "doing your emissary caches" can take different amount of time per day depending on player's skill, class, spec, addons, knowledge of the game and so forth.