It is pretty true of microphyllas, greggiis, and most other shrubby new world sages.

No plant ever 'needs' deadheading; deadheading is a need created by those of us who grow the plant and want it to look or grow a certain way. So, based on that I'd answer your question with a 'no.' However, my Hot Lips plants are growing in front of an office building, and every 4 or 5 months they begin to look a little run down, blooming tails off, and I would argue that they need deadheading. They are also too large for their space by this time. I have seem similar things from greggiis and other microphyllas; every few months they need some dead stems cut off to look their best. On the other hand, I have negelected to give them this trimming at times for a year or more and they still look fairly decent, just not as good as they could.

The only one I always deadhead is the hybrid Raspberry Delight. It blooms with such fury in June and July that be August it becomes a mess a spent flower stalks. Right now the greggii Wild Things could use some attention for the same reason.

I must admit to taking the garden shears to all my mature micros, greggs and hybrids thereof! By mid July-August they are inevitably looking leggy and a rather untidy.

I don't have the time to snip off only the older flowering stems and consequently, with a shearing taking off up to 1/4 of the plant, I lose all the flowers for about three weeks. However I am then rewarded with a great fresh showing by the autumn.

I've done this for years and the plants don't seem to suffer.

Jim