It's always your decision since it's your body and future at stake. The EP is just offering his/her studied advice based on their experience and learning.
The best EPs that I know of suggest a Watchman anyway, despite the success of previous or future ablations, because the disordered heart is permanently disordered. Just because the EP blocks the extra signals from causing your atrium to beat chaotically doesn't mean you don't still have that disordered state! And further, the disorder tends to progress for all but a very few people. This means that many of us, if not most of us, can expect to experience ectopy again in the future. For some, it happens inside of a year, for others it might be as long as ten years. But it happens so often that it's almost a given for the majority of AF sufferers: once you have it, you have it. And wouldn't it be better to have that Watchman insurance already in place? And save all the DOAC costs during the interim? If the Watchman shows no leakage at the 6 month point (done with a TEE) after a successful ablation, then you can opt to forego any further DOAC. At least, many EPs will agree to that.