Small Stakes No-Limit Hold'em

On page 141:

If your opponent 3-bets light frequently, but is selective with flop continuation bets:

[...]

*) Use a mixed strategy of small 4-betting and calling the 3-bet.
Tend to 4-bet with strong hands and sometimes with weak
hands. Since 4-betting is mostly a bluff, hand strength when 4-
betting doesn’t much matter, except that you must be willing
to get all-in with at least two-thirds of these hands in 100bb
games. Hands with aces in them, such as A3o, are particularly
good weak hands to 4-bet. Weak aces have a surprising
amount of equity against narrow ranges, typically over 30
percent. They are also poor for calling 3-bets with the intent to
push any draw or pair on the flop, because they rarely flop
draws.

Are you saying A-rag hands are good to 4-bet for value and get it in with? I would disagree, it might be good to bluff with due to card-removal though. Did i misunderstand the text? Did you mean 4bet shoving pre-flop?

Also the following sentence from the quote above i dont understand:

Since 4-betting is mostly a bluff, hand strength when 4-betting doesn’t much matter

when you explain several times that the 4bet-bluffs should be balanced at least with double as much value 4 bets (1/3 bluff, 2/3 value). Can i understand this as "When 4 bet bluffing the hand strength doesnt matter as the opponent will likely shove or fold."?

Thanks for your help and this great book!