Interesting, in that for some reason we've had them as incorporeal since day one.
Looking at the 1e MM the illustrations for both Spectres and Wraiths very strongly imply incorporeality: the Spectre is obviously at least semi-transparent and the Wraith is shown as a wafty-looking dark thing with no legs.
This is later backed up by the UA Illusionist spell Wraithform, which specifically states the target becomes insubstantial and can pass through tiny openings or cracks and otherwise implies the target becomes a Wraith in all ways except attack forms.
Its interesting in that spectres look a lot like they were intended to be Nazgul ringwraith stand ins, relatively top tier scary undead. But ringwraiths ride mounts and wield weapons. Whether spectres could pick up objects or not and whether they could walk through walls or not seems undefined in AD&D.
In OD&D however spectres explicitly were incorporeal.
SPECTRES: These monsters have no corporeal body which makes them totally impervious to all normal weaponry (but can be struck by all magical weapons), including silver-tipped arrows.
In contrast OD&D wraiths were simply more powerful flying wights that other than the name you would not expect them to be incorporeal from their description.
WRAITHS: These monsters are simply high-class Wights with more mobility, hit dice, and treasure. Hits by silver-tipped arrows will score only 1/2 die of damage, and magic arrows only score 1 die of damage when they hit.
The 1e wraithform spell makes it sound like wraiths might be more like vaporous smoke that needs small openings than incorporeal that can go through solid walls, but this could just be the spell form acting only fairly similar to the actual nature of wraiths.
Wraithform (Alteration/Illusion)
Level: 3 Components: S, M
Range: 0
Duration: 2 rounds/level
Area of Effect: The illusionist
Explanation/Description: When this spell is cast, the illusionist and all of his or her gear become insubstantial. The caster can be hit only by magic weapons of + 1 or better, or by creatures otherwise able to affect those struck only by magic weapons. Undead of most sorts will ignore an individual in wraithform, believing him or her to be a wraith or spectre, though a lich or “special” undead may save versus spell at -4 to recognize the dweomer. The illusionist will be able to pass through small holes or narrow openings, even mere cracks, with all he or she wears or holds in his or her hands, as long as the spell persists. No form of attack is possible when in wraithform, except against creatures which exist on the Ethereal Plane, where all attacks (both ways) are normal. Dispel illusion and dispel magic are the only ways to force an illusionist in wraithform back to normal form. The spell caster can return to normal form at will, but this ends the spell effect. The material components for this spell are a bit of gauze and a wisp of smoke.