It's true that the two words "lean" and "incline" CAN have similar meanings. But not through the examples that you cited.
First, if we talk about Parts of Speech:
lean = Verb, Noun, Adjective
incline = Verb, Noun
In your examples, "lean" is an Adjective and "incline" is a Verb, and in these forms they don't share much similarity:
lean (Adjective) = thin, not prosperous, tight, not productive etc.
incline (Verb) = to slant, to have a tendency etc.
If you change the Parts of Speech though, you might find what you're looking for:
leaning (Adjective) = tilted
ex. the leaning Tower of Pisa
inclined (Adjective) = slanted
ex. an inclined plane
lean (Noun) = an angle
ex. a pronounced lean
incline (Noun) = a slope
ex. a steep incline
Finally, the Verbs are not so similar:
incline (Verb) = to slope
ex. The land inclines.
lean (Verb) = to be stand at an angle against something for support
ex. The wall leans.