SEMRush data discrepancy

I've been comparing a few SEO tools and noticed a significant discrepancy in monthly search volume for a specific keyword between SEMrush and DataForSEO. DataForSEO apparently uses Google AdWords data, while SEMrush states they use a combination of sources. However, the difference is quite large—40 searches per month vs. 100. I haven't been able to confirm whether SEMrush excludes CPC data, which could explain the variance. I understand that different tools rely on distinct metrics and databases, but such inconsistencies make me question the accuracy of the search volume data. Since decisions are based on these numbers, I want to ensure I'm using the most reliable source. Any insights on this would be appreciated.