I believe water temperature, amount of sunlight penetration, water level fluctuation has a lot to do with the spawn. I also believe if Crappie have small hard yellow eggs in them at this time, something went wrong with their spawning process and those eggs will not be laid in a natural spawning process. I am no expert just what I have observed over 60 years. Here is what TPWD has to say: https://tpwd.texas.gov/publications/pwdpubs/media/pwd_br_t3200_178.pdf

I will say this respectfully. I believe a lot more of what fisherman who have had personal experiences have to say, especially over many decades... there simply havent been very many detailed, controlled studies done by TPWD. yes they do population studies, which are only effective on some lakes, deep lakes are very hard to measure . nets and shocking doesnt work in deep water. purse nets do, but they dont use them. Many myths have been repeated over and over thru the years.
most folks in thier ,50,60,70s recall when the main sources of information came from fishing magazines.
they were gospel when fishing information was concerned. Many notorious fisherman who were considered successful, wrote articles, and because they produced fish, almost everything they wrote, was considered true and correct.
As humans we tend to always come up with a reasonable answer to a question, even though we are not 100 percent sure of that answer to be fact.. we want to be respected for our knowledge.
also in many instances, those writing the information, actually believe, whole heartedly that what they are saying is 100 percent true and correct.
Personally after fishing the spawns for many years, I have found it to be a complete and total myth that water temp governs when and where crappie will spawn, or that water depth governs when and where they will spawn.. my spawn catch results are no longer hit and miss with more miss than hit as in years gone by, they are mostly hit now that I dont believe the myth anymore.