Yeah, chewing doesn't make a big difference, especially tiny little tablets like codeine phosphate 30mg.
With the tablets being so small, by chewing them you'd probably end up with half your dose stuck in your teeth!
I would chew 30mg DHC a bit, just crunch them up into a few pieces, but I didn't notice a difference really. It's just a habit of mine to chew pills, especially benzos, but I semi sublingual them anyway cos I like the taste and they hit faster.
Only pills I wouldn't bother crunching up before swallowing is zopiclone, those tiny codeine, and non recreational shit like paracetamol, antibiotics etc.