The removal of that exception to exclusion l. is a problem for the insured.

With that exception, if the named insured becomes liable for damage due to work performed by a subcontractor, the exclusion would not apply; neither would the exclusion apply to the named insured's liability for damage to the subcontractor's work. But, without the exception, if the subcontractor's faulty wiring or other work causes an entire building to burn down, and the general contractor is sued for the entire loss, the general contractor's CGL form will not apply to the claim.

The exclusion (l.) applies to property damage to the named insured's work arising out of it or any part of it. The named insured's work includes work done for him by others. So, the property damage in this case was to the named insured's work, and it arose out of that work, or at least a part of that work. And, without the exception for the subcontractor's work, the exclusion will prevent coverage for the property damage claim.