Yes, most of the Companies doesn't encourage leave during notice period.
In your case the extension should be the number of days leave availed by the employee only and not including the in between holidays (sandwich leave).
Also the general practice followed among companies is either extension of notice period or LOP for the number of days leave availed. Not both.
10th May 2019 From India, Madras
Its not fair HR Practices of a company that an employee who will be going away from organization is not allowed to utilize leaves due to his credit. The fair practice would be to allow resignee pro-rata leave during notice period as he would have been otherwise in employment. Suppose, he has month's leave entitlement PL-2.5 DAYS,Sick leave-0.75 days and CL=1/2 DAY, ie total of all leaves =3.75 days, this he would earn and may avail in a month, should be given as approved leave. Justification and Logic is understood for you, me and whole world. If notice period is three months, similar formula but ensure that he does not remain absent and applies leave same month. The leaves which will be availed by exiting employee is subject to necessary sanction of HOD.In case, employee avails leaves as suggested above and does his work without causing any work suffer, he may be allowed more leaves out of his leave balance with unspoken message that it is a good will gesture and management discretionary powers for promotion of employees dedication and in recognition of good performance.As observed, this is as a matter of rule generally practiced by good organization and employees feel communicated, satisfied and they carry a good image with them.
Future Instt.of Management and Technology, Bareilly (U.P.)
Labour Laws Adviser
Navtarang HR Services
10th May 2019 From India, New Delhi