Would emphasize your point around services - SaaS investors are generally allergic to this stuff and prefer services to make up as little of revenue as possible. It's typical low margin and not seen to be very "strategic" (though this could be debated).
SaaS is also much easier to analyze and diligence than the typical non-SaaS software company or consumer internet business. I won't say it's dead simple, but it's very much not rocket science. In combination with excess capital, this leads to prices getting bid up as such ease of diligence leads many investors to throw in a term sheet. It's just so easy to get comfortable with this stuff.
One caveat to all this that ties to your last point around the market / economy is volatility. You can see in the data that companies that generate a higher amount of the their growth from SaaS-like retention/upsell see higher valuation volatility when the market turns for any reason. [1] The "best" SaaS companies in the eyes of later-stage investors are typically those with high net revenue retention - but these are also the ones that get whacked the most in corrections.
As far as a downturn taking down growth equity - time will tell.