Melee or Ranged attacks by Monsters, no distinction in modifiers?

Weapons with the Thrown property can be utilised as both a Melee as well as a Ranged weapons. When used as a Melee weapon you base the attack+damage rolls on Strength, otherwise on Dexterity (unless it’s a Finesse weapon, in which case you decide).

My question:

1) Why don’t I see this reflected in Monster statblocks? I’ve been going through the MM, and never have I seen this reflected (ie. the attack and damage are not specified specifically for melee/ranged attacks). Is this to keep it simple, or shouldn’t you make this distinction when it comes to Monsters? And thus:

2) Should I follow the attack roll and damage from the action as described, or calculate it differently depending on if the attack is a melee or ranged attack?

For example, looking at the Ogre (MM p.237), it reads for the Javelin:

Javelin. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 30/120 ft., one target. Hit: 11 (2d6 + 4) piercing damage.

Since the Ogre has a +4 Str and a -1 Dex, the attack and damage rolls are clearly based on Strength. Now, what if this Ogre decides to hurl that Javelin at someone, should I use these numbers or figure out that the Ogre is a CR 2, thus has a proficiency bonus of +2, thus the Attack roll would become +1 (2-1) and the damage roll -1?

Bonus question. Sometimes the “or Ranged” is left out from the action description for weapons that have a Thrown property. Does this mean that this monster doesn’t want or cannot make a ranged attack (the Kobolds dagger attack for example, MM p.195)