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Class names are part of CSS code, therefore crawlers read the class names.

While 'class names' are not considered in ranking factors specifically, there are other factors that are impacted by them. In addition to issues related to robots.txt files disallowing a crawl of the assets and directly harming how well Google algorithms render/index content, resulting in suboptimal rankings." [c] Here are a few more items to consider:

• External resources like CSS & JavaScript help algorithms understand that the pages are optimized for mobile. And this is a factor in ranking. [b]
• Some JavaScript removes content from the page rather than adding, which prevents Google from indexing the content. This is also a factor in ranking [b]
• Speed is a factor and google publishes a CSS/HTML style guide and best practices for faster loading pages, to optimize the serving of CSS / number of calls. [a] [e] 

I'd take the Simon Sinek approach to this -- to ask you

• why is you/your client interested in this workaround for Hubspot?
• What do you gain by keeping it on the subdomain?
• What would you lose?

Assuming most people here would agree the important factors (as SEO technologists) in order are:

1. Is the site reachable?
2. Is the site readable? (googlebot et al)

To date, (from what Hubspot has communicated with us)  there is yet to be any way to set up Google Webmaster tools legitly, without creating two sites (seemingly competing for the same keywords) for both the 'blog.website.com' and the 'website.com' as one would do for a typical 'www.website.com' sub-domain (google has you choose the primary and it's also indicated in analytics).

Assuming it's similar to my client work/experience, your client wants wants:

• Hubspot data
• CTA buttons
• landing pages

Thus far, I don't see any reason any site should use the Hubspot platform w/ subdomain.  The true alternative is setting up wordpress as one normally would, then installing the Hubspot plugin.  So far (about six months) this has done the job.

Before we made this change for our clients we were constantly running into issues which caused me to question the legitimacy of a tool, even a company, that encourages site set-up / blog settings, that contradict what GWC (Google Webmaster Central) has advice their community.  Furthermore, seemingly sees no issue/s with all the above, including the challenge of setting up a site with a secure cert added after a site has been set up on Hubspot.  Again, 'httpS' causes issues with their 'sub-domain' approach to the blogging aspect, even to the extent they have told my client that they would have to re-purchase the secure cert from them to make the 'marketing' subdomain also secure.  So far, their organic search traffic is up by 7,000+%.

Interested in what others are doing as well.  It has been quite a journey but certainly a learning experience. 
Cheers to learning!

Christine and I are working on this project together and my ongoing concern is not so much if they get credit passed on to them (logically I would think if domain owners could do this, it would be considered a no-no by google) yet more so if it detracts in any way from the main URL.  i.e. diluting the value of the content on the main URL because it competes for the same keywords, etc. therefor 'siphoning' link credit.

This is my first time working with a tool like Hubspot and I feel strongly that it does more SEO harm than it does good. However, my lack of knowledge in the area of Hubspot could be why I feel that way.

So as a follow-up to Christine's question, does one lose any credibility or get diluted by putting said blog on a subdomain rather than in a subdirectory folder?

Thanks so much in advance!

Christine and I are working on this project together and my ongoing concern is not so much if they get credit passed on to them (logically I would think if domain owners could do this, it would be considered a no-no by google) yet more so if it detracts in any way from the main URL.  i.e. diluting the value of the content on the main URL because it competes for the same keywords, etc. therefor 'siphoning' link credit.

This is my first time working with a tool like Hubspot and I feel strongly that it does more SEO harm than it does good. However, my lack of knowledge in the area of Hubspot could be why I feel that way.

So as a follow-up to Christine's question, does one lose any credibility or get diluted by putting said blog on a subdomain rather than in a subdirectory folder?

Thanks so much in advance!