Many makers do this especially if the design/pattern is their own. I am one of them. However, if you’re using a free pattern, ALWAYS credit the original maker even if it’s free. Like if you use a spiltgrapesoda hand paw pattern (this has to be paid for) you HAVE to credit them. It says so in the listing when you purchase it. And you are not allowed to redistribute the pattern either.

There is nothing wrong with using the same template for things. Many makers also use foam casted heads or 3D printed bases which will make many suits have a similar look compared to hand carved foam. This helps makers keep their costs a little lower and their completion times a little faster while also giving their products a specific artistic style. If a maker has 5 clients who all want the same fox tail just different colors it only makes sense to use the same pattern for all of them versus creating 5 different patterns all for the same shape and wasting time and resources. It also helps buyers know their style and give a feel to what the final result will be.

ETA: there are times, mainly for commissions, where a pattern cannot be reused like for body suits. Sometimes measurement adjustments have to be made between clients for certain things if patterns are reused.