Depreciation and profit and loss on sale of asset are both different in accounts as well as income tax.
In accounts, each asset is a separate asset and each asset is individually depreciated and profit/ loss on sale of asset is individually considered.
Whereas in taxation, block of assets method is followed and gains/ loss is considered only when
1. Block is empty and closing balance of the block turns positive (stcl)
2. Block is empty and closing balance of the block turns negative (stcg)
3. Block is not empty but closing balance in the block turns negative (stcg)
Now, in the present case, as per accounts, depreciation on each asset will be separately calculated and in case of 2 wheeler, there will be depreciation for 2 years and 7 months (suppose say rate for 2 wheeler was also 15% wdv) then in such case there would be a profit on sale of asset. It could not have resulted into a loss anyhow.
Secondly such depreciation would be added back and profit so derived would be subtracted while computing profit from business in income tax. Depreciation as per it act will be separately calculated and deducted from profits while computing profits from business.
Depreciation as per IT act will be 15% block and 10% block separately. I.e individual identity of p&m, 4 wheeler and 2 Wheeler is lost. Depreciation will be calculated on closing wdv(cl. wdv = op. wdv + purchases - sold).
Hence sale of 2 wheeler would not result in any profits/losses as per it act. Hence as per accounts, any gains or losses would be adjusted accordingly to arrive at profits from business.
So ideally your auditors are partially correct