The de facto 'what's possible' for ability scores is 3 to 18. The character creation chart has nothing higher than an 18. Comparing PCs with an ogre is imperfect, in part because monsters are handled differently than in many other game systems, flat out not going by the same rules as PCs.
I understand it would be helpful to have a 'true' answer from Mr. Goodman himself, but if it turns out you don't like his answer, do you then like the game less?
Part of the ethos of the game is that you define and run things how you want them for your campaign. You can change things up from one campaign to the next. Some folks like 'superhero' dungeon delvers, and some prefer 'merely mortal' delvers. The game lets both groups have their cake, and eat it, too.
Lot's of ideas have been bounced around; why not just go with what you feel is more fun to play: capped at starting value, capped at 18, no cap at all, cap at starting value unless magic is happening, etc. etc. etc.
Gnome Boy (a.k.a. "Jon") • DCC play-tester @ DDC 35, Feb 2011. • Beta DL 2111, 7:00 AM PT, 8 June 11.Playing RPGs since 1977
• Quasi-occasional member of the Legion of 8th-Level Fighters.—Here Be DCC Monsters—VOORAK, L, Hunter, S10, A12, Sm10, P6, I13, L15, AC 10, HP 3, Spear +0 1d8, Init 0; R 0, F 0, W -1, Holy water, Pelt, 3 iron spikes, 1d ration, 4-leaf clover (Find secret doors) (+1), Com +1
SARKLA, C, Gatherer, S9, A14, Sm14, P15, I14, L8, AC 11, HP 5, Knife +0 1d4, Init 1, R 1, F 1, W 1, Chest, Basket of veggies, 2d ration, lg sack, waterskin, torch, Seventh son (Spell checks), Com +1
TARR, C, Hunter, S14, A11, Sm15, P13, I8, L8, AC 10, HP 3, Spear +1 1d8+1, Init 0, R 0, F 1, W 1, Holy water, Pelt, 4 torch, flint/steel, 1d ration, sm sack, Fox's cunning (traps), Com
TELVA, N, Herbalist, S13, A6, Sm9, P6, I12, L10, AC 9, HP 2, Club +1 1d4+1, Init -1, R -1, F 0, W -1, Chain 10', Herbs- 1 lb., 50' rope, 2d ration, torch, Speed of cobra (Init), Com