So we are agreed ALL words are phonetically regular
No.
Some sounds, like the short a of cat sat mat, have very few exceptions (plaid, plait, have, meringue), and can be said to have an almost completely regular spelling.
The long oo sound on the other hand is spelt with oo only in half of all common words, it is therefore completely irregular:
Brutal, brute, crucial, crude, fluent, fluid, Fluke, flute, frugal, glucose, guru, intrude, jubilant, July, June, Jupiter, Jury, Juvenile, lubricate, ludo, ludicrous, lukewarm, luminous, lunar, lunatic, plural, prune, recluse, ruby, rude, ruin, rule, rural, secluded, truant, truce, truly, truth, Zulu. Gnu. Bruise, cruise, sluice; fruit, recruit.
Acoustic, bivouac, boutique, coupon, group, recoup, route, soup, toucan, tourist, troupe, wound, youth.
Shrewd, strewn. Brew, crew, drew, grew, screw, shrew, slew, strew, cashew. Clue, glue, rue, true, accrue, construe. Do, lasso, who. Tomb, womb. Lose, move, prove. Gruesome. Manoeuvre. Sleuth. Canoe.
Blew/blue, flew/flue/flu, poo/pooh, shoo/shoe/choux, threw/through, too/to/two, you/ewe/yew.
Baboon, balloon, bloom, boom, boon, boost, boot, brood, broom, cartoon, choose, cocoon, cool, doom, droop, food, fool, gloom, goose, groom, groove, harpoon, hoof, hooligan, hoop, hoot, lagoon, loom, loop, loose, loosen, loot, macaroon, maroon, mood, moon, moor, moot, mushroom, noodle, noon, noose, pontoon, poodle, pool, poop, poor, proof, roof, room, root, saloon, school, schooner, scoop, scoot, scooter, shoot, smooth, snooker, soon, soothe, spoof, spook, spool, spoon, stool, stoop, swoon, swoop, tool, tooth, troop, whoop, zoom. Boo, coo, goo, loo, moo, woo, zoo, bamboo, cockatoo, hullabaloo, igloo, kangaroo, shampoo, tattoo, voodoo, yahoo.