Yes. A tile that looks right can still be unsuitable for the slope on which it has been installed. Choosing a covering starts with the roof and the product specification, not just colour or appearance.
The product name needs to be specific
Manufacturers set conditions for the use of their products. Marley distinguishes standard Mendip tiles from Mendip 12.5, with different pitch limits and other requirements. The precise variant, finish, headlap and roof dimensions matter. A description such as “low-pitch tiles” is not a complete specification.
Why a surface fix may not address the problem
If the covering has been used outside its specified conditions, sealing one visible point does not change the roof pitch or make that covering suitable. The assessment should establish what is installed and whether the arrangement is appropriate. Do not assume a membrane underneath makes any tile suitable for any slope.
A real Crosby example
On our Crosby extension project, the existing tiles were unsuitable for the pitch. We replaced them with low-pitch Mendip tiles and replaced the roof window as part of the work. The project report shows the job; it should not be read as a claim that the same product is suitable for every extension.
What to request in your quotation
Ask for the intended covering, the basis for its suitability and the treatment of roof windows and adjoining walls. We would rather decline an unsuitable specification than install a covering simply because it is the one a customer hoped to use. If the current roof leaks repeatedly, share that history when asking about replacement.
Technical reference: Marley: Mendip and Mendip 12.5 product requirements. The requirements for an individual roof need checking against its actual specification.