You do have to list on the application form that you saw a GP, but as you were on a visa that entitled you to 'free' NHS care, you don't have to do anything else or worry about this.
They are just trying to make sure that people who used the NHS but were not entitled to free treatment have paid for that treatment.
It's not about whether you had any treatment or not, it's about whether you had to PAY for that treatment... because if you have £500 or more in unpaid NHS debt (I.e. From treatment on a visitor visa), it is an automatic visa refusal.
On a student visa valid more than 6 months, you did not have to pay at point of service anyway (as you paid the IHS), so this will not affect you at all.
Just list your GP visits and the GP details and state you did not have to pay due to being on a Tier 4 visa.
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