Section 80ddb

Provisions of sec 192 apply for TDS on Salaries and according to the provisions for the purpose of determination of amount of Tax at source deductions under chapter VI A are considered and 80DDB is covered u/c VI A

Nope, his contentions are not justified. Make him read this

Para 5.4 Deductions under Chapter VI-A of the Act - The following deductions under Chapter VI-A of the Act are available:

Under section 80DDB, where an assessee who is resident in India has, during the previous year, actually incurred any expenditure on the medical treatment of such disease or ailment as may be specified in rule 11DD made in this behalf by the Board

https://law.incometaxindia.gov.in/DitTaxmann/IncomeTaxActs/2009ITAct/sec_192.htm

Provided that no such deduction shall be allowed unless the assessee furnishes a certificate in such form and from such Authority as may be prescribed. The form is Form 10-I, and the Prescribed Authority is any doctor registered with the Indian Medical Association and holding Post-graduate qualifications.

For the purposes of this section, “dependent” means a person who is not dependent for his support or maintenance on any person other than the assessee.