ok this is changed in next update but its easier to get your sugarcanes to 10's and then mutate your metal seeds with your sugar canes as the newly created seed which has to be a metal seed since sugarcane cannot grow on dirt. and this new seed will be somehting like 6/6/6 and then replant again and it'll be 8/8/8 and then again it'll be 9/9/9 and last time it'l be 10/10/10 this is a bit cheaty but it puts you on the fast trackThis pack has nowhere near enough content to wait until a single seed mutates to 10/10/10, and the horrible advice is telling players to go sleep or something while the plants grow. The moment you get those 3 seeds is not in the long run, it's in the beginning where your quests are stuck until you get iron or copper.
That's where you need actual iron, not 10/10/10 seeds, and that's where you need the 3 seeds (or more if you make more seeds yourself, which is a good idea). If you take them, you won't be stuck on the quests, and you won't feel any grind. You'll be doing your "something else" while growing and farming 3 seeds. If you instead just use one seed, based on some OCD-inspired desire to have 10/10/10 seeds *before* you start using the iron, you'll be waiting so long that you'll get bored with the modpack (you maybe won't, but the guy you gave the horrible advice might).