Even 5k + 30s feels very hard for a tempo

I ran 14:32 and would do longer tempos around 5:20 pace (occasionally faster). It doesn't need to be 5:05 unless you are ready for that.

The biggest mistake I see from college coaches (and pretty much all coaches) is having their athletes run tempos/progression runs too hard. Definitely happened to me...

how well do you typically train compared to racing? I have kids who can't run 8x65 seconds but can run 4:10 for a 1600. vo2 max paced 800s would be impossible for them. And the same holds true as you go up the line.

Or maybe you are very strong anaerobically, so you can power your way through a 5000, but any distance longer is very weak, so a hypothetical "threshold" or "tempo" pace doesn't really work for you.

Or maybe it's just mental. Do you keep track of heart rate?

You are running your tempo too fast. A tempo pace should be a pace you can run for about 60 minutes. Based off of your 5K pace, you are running your tempo at 10K race pace 5:05 / 5:25 is your tempo pace - good luck

With professional level training Tempo is about mile pace +45 sec; with semi pro training, mile + 1 min.

Tempos espoused by some well known sources are near impossible for most people. You have to be really motivated and have people to run with to approach what some believe is "tempo" pace in my experience. Fortunately, running a "slower tempo" is a fine workout too.

Well start 5k + 30s is pretty darn aggressive for a tempo. A lot of people think that's too fast. We, along with other programs that have had lots of success with tempos that are "uncomfortably hard" though.

A lot of our top runners run about 30 seconds faster than their grass 5k pace, but we are doing it on a flat hard surface.

Could be a sign that you are underdeveloped aerobically (although you are a sub 15 5k runner, so maybe not). If you really want your tempos to be better, do them more often, do them at the pace you want, but split into chunks, and do them longer, but slower and your body will adapt.

I have broken 4:10 but barely broke 15. My tempos are at around 5:25 as I'm still developing aerobically due to low mileage and being more of a mid-distance talent anyway.

A while back I said a lot of tempos are basically race efforts and got down voted for it. I see many on strava racing barely 10 seconds per mile faster than "tempo". In my opinion its a dumb workout.

Because you are not fit enough. Run slower until you are.

for a 1445 runner, 525-535 IS a tempo. Keep on running your tempos, and run them by effort, disregard pace.

Why does it matter?

Do you want to be the best tempo runner you can be, or do you want to get the best results in races?

Running at true tempo will better assist you in achieving the latter. In addition, training at your actual lactate threshold will likely improve it more than training at a higher intensity.

my tempo pace is like 40 sec- 50 sec slower than 5k.