They could have used flags for regular missions while they used full data for downloadable missions.
By the way, looking at entry 36 in the games text (a/0/0/2) you will find a list of all 45 regular missions with their descriptions.
But there is also this:
At least Women at Pokémon Centers, Pokémon-Quiz Championship!, Rare Pieces!, Find Rare Berries! and Find Pokémon! were available as event missions!
Find Rare Berries! - Rare Berries have been discovered!\nLook for shining places in forests\nand caves, and collect Berries!
Rare Pieces! - Get rare items that are said to\nhave been made in ancient times.\nLook for shining places in caves\nand on roads!
Berry Festival! - Rare Berries have been discovered!\nLook for shining places in forests\nand caves, and collect Berries!
Women at Pokémon Centers - Speak to Pokémon Center women\nin towns and on roads.\nThey might give you a\nwonderful present!
Pokédex Quiz! - Speak to Scientists in towns and\non roads, and answer Pokémon quizzes!\nYour knowledge as a Trainer\nwill be tested!
Shopping Impossible! - Again, men wearing black!\nBuy, buy, buy very rare items!\nBut watch out for the prices!
Endless Battles! - Try endless training with Veterans!\nDefeat <NUMBER> or more Veterans\nwithin the time limit!
The Pokémon Center Quiz Champion! - Speak to Scientists in towns and\non roads, and answer Pokémon quizzes!\nYour knowledge as a Trainer\nwill be tested!
The Quiz-Champion Finals - Speak to Scientists in towns and\non roads, and answer Pokémon quizzes!\nYour knowledge as a Trainer\nwill be tested!
Pokémon-Quiz Championship! - Speak to Scientists in towns and\non roads, and answer Pokémon quizzes!\nYour knowledge as a Trainer\nwill be tested!
Gifts from Pokémon Center Women - Speak to Pokémon Center women\nin towns and on roads.\nThey might give you a\nwonderful present!
Find <POKEMON> - Find <POKEMON> in rustling grass!\nWhere are they?\nShould you use the power of\nPass Power?
Find <POKEMON> - Find <POKEMON> in rustling grass!\nThey may be on Route 5?
Find Pokémon! - It has been reported that\nuncommon Pokémon were found!\nVisit Hidden Grottoes in different\nareas, and find Pokémon!
Find Hoenn Pokémon! - Pokémon from the Hoenn region\nseem to have been found in\nHidden Grottoes! Visit Hidden Grottoes\nin different areas, and find Pokémon!
Battle Pokémon! - Go to Hidden Grottoes in various\nareas, and find Pokémon!\nRaise them, and they will shine\nin Pokémon battles.
This doesn't have to mean anything though! I doubt we can force load them.