8 – Is it acceptable to pass data from a module to a model?

I'm trying to transfer data from a block module into a template. I found that I could create a rendering array property and then access it in the model. Here is an example of my code:

the class MyBlock extends BlockBase {
return [        
        '#firstname' => 'John',
        '#lastname' => 'Doe',

I can access this data in the twig template using:

{{Elements.myblock.content['#firstname'] }}
{{Elements.myblock.content['#lastname'] }}

Is this an acceptable way to transmit data into a model? All other examples I've found have rendering tables captured by a hook_theme function, and passed to the model. The method I show above seems simpler and I wonder if it is problematic to do it this way.

Thank you!