It's true that to cite the string of albums wouldn't be accurate evidence of any hard bop proclivities - but I don't think that's what anyone has said...I think people have only suggested that they [subjectively, of course] prefer Morgan's playing in more hard bop-ish sessions. It's of course true that he's on Larry Young stuff, Grachan stuff, etc.
That said, I don't know that Search for the New Land is particularly progressive..?
I also think that 'Sidewinder' is not necessarily the paradigm of hard bop, so to say he felt semi-trapped by it is interesting, but I don't know how much it bears on the thesis that he sounded most comfortable in hard bop surroundings. In fact, even if it were a hard bop paradigm, I think it'd still be a consistent position to say that he sounded comfortable in hard bop, notwithstanding that he felt semi trapped by it!
What I was saying was, Search for the New Land, specifically the suite-like title track is forward looking (not "progresive")incorporating things besides just straight out hard-bop. Aside from that there are his appearances on Joe Henderson's Mode for Joe (1966) his own Procrastinator (1967) and Andrew Hill's Grass Roots (1968) which all definitely contain some hard-bop components but also show that he more than experimented with leaving the hard-bop genre. He accords himself more than well on each outing and sounds completely at home. Also the final Live at The Lighthouse recordings point to a more modal-free approach and an artistic evolution which was cut short.