Reading Tab in Chord/Melody playing

I’m a beginner dulcimer player, and having so much fun with it! I started out looking at free tabs online, and have progressed to buying music books. In one of my books, I read the “how to use this book” section, and my eye caught something that I don’t know if it is standard, or if it is the way most/all tab is written. The way it is written makes it unclear.

It says, “In the interest of avoiding unnecessary clutter, I chose to not place full chords under every note. If only one number appears under a note, it does not mean you play only one string. Assume that you continue to hold the previous chord on the other two strings until the next chord is played.” (Joe Collins, Irish Charms - emphasis his)

Is this the way I should be playing most songs? I’ve tried some doing both, and can see where they both have uses. Some songs, the single notes with an occasional chord sounds fitting and haunting, in others, playing the chords all along sounds joyous and rocking. Is it therefore up to the player, or is there a way to tell? Or do most transcribers like to use the shortcut?