Merriam-Webster shows the different subsenses of learn relevant here nicely:

learn [transitive verb]: 1a(1): to gain knowledge or understanding of or skill in by

• (i) study,
• (ii) instruction, or
• (iii) experience

[last classification labelling, i/ii/iii, mine].

In spite of M-W's ordering here, I'd say that the default subsense is the 'assimilate knowledge, understanding, wisdom ... often not by design' subsense (ie iii) rather than the 'set oneself to learn by study and practice' (i) subsense. So, with this subsense not highlighting application, design, the intensifier 'hard' makes no sense.

• Work / try / practise / play / study / think ... hard.

But not the non-applicational

• *Understand / dream / appreciate / pick up / realise / discover ... hard.

So I'd say you're on the right track ... the complication is that 'learn' is very polysemous.

Merriam-Webster shows the different subsenses of learn relevant here nicely:

learn [transitive verb]: 1a(1): to gain knowledge or understanding of or skill in by

• (i) study,
• (ii) instruction, or
• (iii) experience

[last classification labelling, i/ii/iii, mine].

In spite of M-W's ordering here, I'd say that the default subsense is the 'assimilate knowledge, understanding, wisdom ... often not by design' subsense (ie iii) rather than the 'set oneself to learn by study and practice' (i) subsense. So, with this subsense not highlighting application, design, the intensifier 'hard' makes no sense.

• Work / try / practise / play / study / think ... hard.

But not the non-applicational

• *Understand / dream / appreciate / pick up / realise / discover / learn [default sense] ... hard.

So I'd say you're on the right track ... the complication is that 'learn' is very polysemous.

Merriam-Webster shows the different subsenses of learn relevant here nicely:

learn [transitive verb]: 1a(1): to gain knowledge or understanding of or skill in by

• (i) study,
• (ii) instruction, or
• (iii) experience

[last classification labelling, i/ii/iii, mine].

In spite of M-W's ordering here, I'd say that the default subsense is the 'assimilate knowledge, understanding, wisdom' subsense (ie iii) rather than the 'set oneself to learn by study and practice' (i) subsense. So, with this subsense not highlighting application, the intensifier 'hard' makes no sense.

• Work / try / practise / play / study / think ... hard.

But not the non-applicational

• *Understand / dream / appreciate / pick up / realise / discover ... hard.

So I'd say you're on the right track ... the complication is that 'learn' is very polysemous.

Merriam-Webster shows the different subsenses of learn relevant here nicely:

learn [transitive verb]: 1a(1): to gain knowledge or understanding of or skill in by

• (i) study,
• (ii) instruction, or
• (iii) experience

[last classification labelling, i/ii/iii, mine].

In spite of M-W's ordering here, I'd say that the default subsense is the 'assimilate knowledge, understanding, wisdom ... often not by design' subsense (ie iii) rather than the 'set oneself to learn by study and practice' (i) subsense. So, with this subsense not highlighting application, design, the intensifier 'hard' makes no sense.

• Work / try / practise / play / study / think ... hard.

But not the non-applicational

• *Understand / dream / appreciate / pick up / realise / discover ... hard.

So I'd say you're on the right track ... the complication is that 'learn' is very polysemous.