I don't think it's discourteous at all. I'm pleased for FHB but don't think it's unreasonable to note that a small regional organ builder is not necessarily the real original Mander with their specialities, equipment, noted pipework makers and voicers simply by the virtue recycling the trading name.
I hope they go well but the change of name has not gone down that well with many of their existing customers who have stuck with their 'local' long established firm for years. The name Mander doesn't have the reverance or the reputation down in Kent and Sussex that it has elsewhere because it's not well known in the area.