He can sing in whatever style he prefers.
Also, when recording "Invincible", he had throat problems, colds, because you can tell how hoarse and gritty at some points his voice tended to sound, although still remarkable, for instance on "Whatever Happens" (the climax of the song), to name but one song. His voice may have become grittier indeed, though it can still convey smoothness and clarity, and examples in the replies above are explanatory enough.
And I think that, more than stylizing his voice to sound angrier, he developed it subconsciously, especially since beginning to sing about deeper, more urgent issues of life. His angry, grunty voice accompanied him ever since little and developed with him and his age and life experience, that it became a natural habit. I really think that it is more of a visceral urge determining him to sing angry, shamanic-like, rather than a planned thing. Even in 1976 he would start singing angrily, for instance in "Enjoy Yourself" - to name but one song - , or in the 1978 "Destiny" album, the most relevant example from it being the song "That's What You Get From Being Polite", when he shouts and grunts "It's so dangerous".
I think the feeling and force takes him there, but has a varied style of singing, and his smoothness and clarity and ethereal vocal delivery never faded. A little more self-confidence may be needed at times, but I am absolutely positive that he still has it.
